Pro Circuit T-6 Stainless System (2022 Kawasaki KX250)

The muffler on the stock 2022 KX250 sounds a little too blown out for me in stock form (even when new). The tone of the muffler is not pleasant to the ear, so I crossed my fingers, called Pro Circuit and picked up a T-6 (stainless system) Muffler System to see if it enhances the current engine character of the KX250. Ti-6 and Ti-6 Pro systems are tough to get at the moment so we settled on a stainless system, which can last longer (more durable) than a titanium system. While I had a PC system, I thought it would be cool to give you guys a run down on a couple other mufflers that I have tried on the KX250 and compare those with the PC (see below). Here’s what I came away with… 

Immediately I weighed the stock and PC T-6 mufflers and took notice of how the Pro Circuit system cut just over 0.7 pounds off the green machine so we were starting off well. The next thing that made me happy was that the PC muffler goes on easy and literally took me 7 minutes to change out! Boom! So far so good! After installation I recruited my son to help me evaluate the system as he now has a new found love for the KX250 and a Team Green ride that didn’t exist last year. I made him write his notes down and I told him we would compare both of ours after we have tested this muffler at a few different tracks. We tested the T-6 at Glen Helen, Perris, secret dez tracks and State Fair MX just so we knew exactly what we were getting out of the PC system. 

 When you purchase your T-6 muffler it will come with a spark arrester screen already installed inside the muffler. DO NOT REMOVE THIS! This helps with back pressure and gives the KX250 the RPM response and bottom end that Aden (my son) and I both like. When we took it out the PC system lost some excitement down low and lost a little bottom end. You can however punch a small hole through the back of the screen and then reinstall it. Doing this actually helps give the PC system a little more bottom end/RPM response while still retaining that back pressure that is important for rear wheel connection. 

Ok so now that we got the “tricks” out of the way, how does this PC system compare to stock?. Normally I DO NOT get more bottom end with a PC system (versus stock) on any brand of bike, but I was surprised that I got a little extra bottom end pulling power out of the PC system. RPM response is a little softer than the stock system, but when opening up the throttle out of corners the KX250 (with the PC system) pulls harder than the stocker. Mid range is where you will feel the meat of this power. When accelerating out of the corner and shifting to third, the KX250 doesn't have that “empty” feeling that the stock muffler has at times when the track is tilled deep. The PC system keeps pulling once the KX250 is shifted into third gear and continues to pull harder into the top end. Over-rev is as good as stock and I didn’t notice any loss of over-rev when swapping the two mufflers back and forth. 

 The only real negative I have found from the PC system is I wish it would have a little more low end RPM response, like the stock system. The stock muffler has such great initial touch of throttle which can make the bike feel a little lighter when hopping over bumps or popping out of blown out berms. The PC system pulls better out of corners, but is just a smoother initial touch (AKA, low end RPM response). If you want more low end RPM response and could stand to lose some pulling power then take the screen out of the T-6. Doing this will give you more low end RPM response, but will hurt some mid range and it will not sound as good in my opinion.

Overall Aden and I are pleased with the PC system for the 2021 KX250 and I guess we shouldn’t be surprised as they do have that Kawasaki race team and all. My son surprisingly felt most of the pulling power, but didn’t feel much increase anywhere else, so not bad for a 14 year old squirrel. Hey, Mitch! If you’re reading this, good job! Chanceability that he reads this? ZERO. POINT. ZERO! 

Extra Credit: We tried a HGS and FMF system just to see what we had in the Pro Circuit T-6 Muffler System. 

HGS: The HGS has a bottom end feel similar to the Pro Circuit system but not as good as a mid range pull. The HGS system has more top end than the PC and FMF system, but it takes a little work to get there. If I was riding a sand track, I could see how someone could like this system. Great top end-over-rev. 

FMF: The FMF has more bottom end than the PC system and has slightly less mid range than the PC, yet more the than the HGS. Top End is short and over-rev has slightly less. than stock. 

Yoshimura RS-12 Full Stainless System (2022 Honda CRF250R)

The 2022 Honda CRF250R is a hot commodity and an aftermarket muffler is even hotter. With COVID-19 wreaking havoc on supply, new muffler systems have been a little slow to get released to the consumer. The Yoshimura RS-12 for the 22 CRF250R should be in stock by the time you read this so let’s compile some notes and talk about some points about the new RS-12 system, before you make a 1000.00 purchase on a aftermarket muffler shall we? 

Install:

Installing the new full system took me less than 20 minutes and the instructions were very detailed. All of the parts that came inside the box fit perfectly and it was easy enough that my 15 year old son installed it! In my opinion, Yoshimura is one of the highest quality exhaust manufacturers in the industry. I have been a part of a few R&D departments and I can tell you first hand that the quality, fit and finish of a Yoshimura exhaust is impressive. I wanted the stainless full system because it was less expensive ($909.00) but is a little heavier than the stock muffler system by just over a pound. I didn’t care about weight as much as performance so stainless is fine with me! 

On The Track:

Now to the part that everyone wants to know...Does the Yoshimura help the little red screamer? The simple answer is yes, but who likes simple answers? Not us! With the stock system, the 22 CRF250R pulled nicely bottom to mid-range, but lacked some top end and over-rev. When trying to grunt up obstacles, the engine still needs some help, but the 22 CRF250R is much better than the 21 in this department. This had Yoshimura rethink their RS-12 for 22 and came in with a spec that keeps most of that bottom end/low RPM responds but added mid range meat and top end pulling power. With the stock muffler the Honda still liked to be ridden a gear lower at times in corners (than other 250F machines), and if I didn’t, it took a bit of clutch feathering and more shifting to get the bike pulling hard again.

As soon as I fired the bike up with the new RS-12 exhaust it was clearly a bit louder, not obnoxious, but a nice, throaty sound that was deeper and less raspy than the stock muffler. I tested the stock system back to back with the Yoshimura system on the same days, so it was cool to see the places on each track where the bike really felt different. The most noticeable place the bike felt better was exiting out of corners while accelerating out of tight inside ruts. With the stock system I had to slightly slip the clutch and pay attention more to my RPM’s, all the way up the lip (If there was a jump out of a corner). When I bolted on the Yoshimura system I could leave it in second gear and just use the meat of the new found Yoshimura power to pull me up and over those types of jumps. Some areas of the track I had to be in second gear and then immediately shift into third with the stock system. With the Yoshimura system I could now be in second gear and let it pull that gear longer rather than having to shift. The Yoshimura RS-12 can also recover quicker if you’re in too high of a gear through corners. The RS-12 picks up quicker and makes the bike feel a little lighter through the mid-range. On soft berms the RS-12 allows the rider to stay on top of the soft stuff better than the stock system because of that quicker rev feel. From mid to top end is where you will notice the big difference between the RS-12 and the stock system. You’re able to pull each gear longer and with a harder feeling pull when making that shift. I would even venture to say that the mid rpm response is slightly crisper when in third gear not to mention that recovery feel in third gear through deep corners is notable right away. Bolting on the Yoshimura RS-12 full system will not make your Honda more responsive down low, but I appreciate that it didn’t complete kill that newfound low end that Honda needed for 22. The best part is that the Yoshimura muffler looks much cooler than the stock ones and sounds ten time better. 

 If you have a 2022 Honda CRF250R and feel like you’d like a bit more mid-top end power, I’d definitely look into the RS-12 stainless system. Yoshimura offers three options, the slip on mufflers ($719.00), the full stainless system ($949.00), and the full titanium system ($1259.00). Admittedly none of these are super inexpensive options, but it’s one of the few things in today’s four-stroke world that can provide a true bolt on benefit. 

Brake Modifications And What They Do On The Track

You can only go as fast as your brakes allow you to slow down. That doesn’t sound quite right, does it? But if you don’t have good stopping power on your dirt bike, chances are you will not be able to get around the track or clip down that trail at any reasonable rate of speed without missing your mark or crashing. Most of today’s off-road motorcycles come stock with fairly good brakes and are usually plenty capable for 90 percent of the riders out there. But what about those 10-percenters who want just that little extra or maybe are super picky about how their brake engages or feels? We wanted to “brake” down several ways that you can alter your brakes’ performance to get the most out of that lever and pedal.

Who comes with the best stock brakes, out of all the new off-road machines? KTM has used Brembo brakes, Galfer rotors, and steel-braided brake lines for quite some time. This combination has proven to be the most powerful, yet the most progressive, way to get stopped or slowed down from an off-the-showroom dirt bike. If you’re on a Nissin brake system, using some of these modifications below will get your bike to this point, or using all of these mods will get you past it.

Fixed Or Floating?

A fixed brake rotor is a simple, solid, one-piece rotor. A fixed brake can also increase lever pressure and power but is susceptible to more warpage when hot due to its solid mounting points. Fixed rotors are lighter than a floating rotor, and, remember, rotors are unsprung weight, which is key to a bike’s handling on motocross machines. A floating rotor system uses bushings that attach a mounting bracket to the brake area where the pads grab. The bushings offer a slight bit of play, allowing for a more centered or equal grab by pads, leading to more even pad wear. Also, in case of an impact, floating discs can take more abuse than a fixed disc. However, floating discs are heavier and more expensive.

On The Track: A fixed rotor has a more positive feel at the front brake lever and can be grabby at times. A floating rotor is not as positive and can require a little more lever pressure to help stop the machine, but is also more linear feeling.

Oversize Rotors:
This is the most common of all brake purchases. An oversize rotor can dissipate heat more (due to its larger circumference), increase brake pad life, and increase the stopping power to your front brake lever because of its extra leverage. Most stock competition off-road bikes come with a 260mm or 270mm front rotor and a 240mm, 245 and 250mm rear rotor. Aftermarket brake companies usually offer their “oversize” front rotors in either 270mm or 280mm. When going to a larger rotor than stock you will need to also change the caliper carrier, which usually comes with the rotor.

On The Track: A noticeable improvement in braking power. Note that when going to a larger rotor than stock, the brake can become more responsive (or grabby) to the touch of the lever.

Steel Braided Brake Lines:

Steel-braided lines reduce expansion when the brake fluid gets hot. This keeps the lever engagement consistent and in the same spot over a longer period of time. The life span of a steel-braided line is longer than a standard rubber/nylon line that comes on most machines. You get more consistent feel at the lever, and consistency is key for any rider.

On The Track: Just purchasing a steel-braided brake line alone with your stock brakes can increase stopping power, especially in longer races. With a steel-braided line and oversize rotor the braking power becomes more intimidating to less skilled riders, but faster riders usually love how easy it is to get the bike slowed coming into corners.

Brake Calipers:

Another option for Nissin brake riders is installing an aftermarket brake caliper. A couple companies offer different calipers (Ride Engineering and MotoStuff) that can dramatically increase your stopping power. An aftermarket caliper has pistons that are larger than a stock Nissin caliper, and with this comes increased power at the lever. But unlike just going to an oversize rotor, a caliper can give you a more progressive feel. Going to larger pistons changes the leverage ratio when using the stock 11mm master cylinder that most Nissin-equipped bikes come with (Honda, Kawasaki, Suzuki), so it feels more gradual and less grabby. Flex is also reduced and airflow is increased with wider fins.

On The Track: The front brake lever has a slightly softer feel to it with the Ride Engineering caliper, but braking power is increased and is more progressive. Going to an aftermarket caliper gives you a better feel at the lever for increased tire traction when pulling in the front brake or dragging through ruts/corners over a longer throw. Along with a steel-braided line and oversize rotor it becomes easier to consistently ride faster and get into corners. It is also more lever friendly to all types of skill levels.

Brake Levers:

If you’re a picky rider and want to take it even further for that personal touch, there is the ARC adjustable front brake lever. The ARC lever lets you choose from three degrees of lever ratio that will let you dial in where you want the lever to grab. Some riders like a very touchy lever right at the beginning of its pull, and some riders like the lever to grab closer in to the handlebar. With the ARC adjustable front brake lever you are able to dial in your personal setting.

On The Track: This is for the pickiest of riders. If you love to tinker and really dial in your lever engagement placement, this is a great lever. It comes in aluminum and Memlon materials

Brake Fluid:

People often ask if they should use DOT 4 or 5 brake fluid. There is nothing wrong with sticking to DOT 4 brake fluid. Its boiling point is plenty high for any modification that you have read about here. However, do not mix DOT 4 and 5 together. DOT 4 is a glycol-based oil and DOT 5 is silicone based. If mixed, your brake will start to feel mushy and less powerful. DOT 5.1 is glycol based and can be added to DOT 4 if necessary, but it is also wise to flush your brake fluid out completely before adding anything different.

On The Track: No performance difference was felt on the track with DOT 4 or 5 brake fluid, but the lever can feel less spongey when going to fresh fluid.

Brake Pads:

Many companies offer the option of brake pads made with different types of material to alter the response and power of the pads’ feel.

On The Track: After some time riding on rotor-kit-specific brake pads and using stock OEM pads, I say stock pads usually wear more consistently (longer) and have a less grabby feel than most aftermarket pads. Some sintered pads were as powerful as OEM, but nothing proved to be any better than a standard OEM brake pads. We experienced more noise (squeak) on some rotor-kit-specific pads when dragging the brakes, more so than OEM pads. Riders who are known to be brake draggers preferred sintered pads, as heat buildup wasn't quite as bad as OEM pads that were not sintered.

What Do I Think?

All of these mods above will help your stopping power, but it is how you want that stopping power delivered that should guide you on which of these mods you make to your machine. If you feel like you have enough braking power, then by no means do you “need” any of this stuff, but if you would like to stop quicker and maybe be able to dive into a corner harder, one of these mods could be advantage. I normally will not do all of these mods together, as I normally would stick to one or two of these per machine at most.

Akrapovic Evolution Muffler System (2021-2022 Honda CRF450R)

I had the initial impression of the Akrapovic Evolution muffler system as I was doing a MotoConcepts/Bullfrog Spas Honda team test. I noticed that they have been running Akrapovic systems on their bikes, so I asked if I could borrow one to see how it worked. Akrapovic's Evolution line is their full titanium muffler system and includes more in the complete package than other system that I have unwrapped. The welds are beautiful and to me the quality of the complete system is second to none. Installing the Akrapovic takes a little bit of finagling, but with some patience it does line up and fit well, as long as you leave most of the bolts loose when installing. 

Once out on the track is when I realized that this Akrapovic muffler system could actually help this Honda chassis calm down just like it did to the 2020 chassis. The Evolution system lets the Honda’s engine roll on smoother at low RPM’s and that smoother feel helps the rear wheel connection as well as provides less pitching (off throttle) than the stock system. AKA MORE COMFORT!!! The Honda CRF450R now builds a smoother roll delivery and a pulling power that is longer through the mid range than the stock system. This type of character can allow you to use second gear in corners more because the second gear hit is not as abrupt or quick and that doesn't upset your technique or the chassis. The Akrapovic also allows the rider to shift later out of the corner with its increased over-rev capabilities. Pulling power up top is increased slightly as your shifting points can be altered now because of the longer pull in each gear. The mid range recovery of the Akrapovic is not as good as the stock system, but honestly that is not a bad thing. The Honda has so much power to work with that a little less “hit” as well as “recovery” actually helps me roll my corners better and allows me to be more aggressive on the Honda. I want to be able to ride this red bike and not let it ride me after 15 minutes into a moto. The Akrapovic system relaxes the engine as well off throttle. There is not nearly as much engine braking with the Evolution system and that also helps your fork from feeling harsh on small de-cel bumps.  

The pitch of the Akrapovic is ridiculously quiet when on the track and will almost give you that MXGP sound and feel. It still has that racey, crisp sound, but just not that raspy high pitch tone of the stock muffler. I was normally a map two guy with the stock muffler, but with the Akrapovic installed I am now a map one guy all day long because of the added rear wheel/friendlier connection. The only other muffler that I have tried that made a big difference on this bike was the FMF system, but this system really gives you a wider pulling power than the FMF. 

The Evolution muffler is the largest possible muffler for the space available. This allows increased sound silencing, which mitigates the impact on the natural environment while also facilitating improved flow for the exhaust gases to make their way from the combustion chamber with as few restrictions as possible. The added strength created by the design aids durability and provides enhanced resilience in the most demanding conditions. The Akrapovic mufflers have been one of the toughest mufflers that I have encountered over the past couple years when I have tested them! Akrapovic muffler packing usually outlasts others and to me just feels like quality stuff.

The Akrapovic system will save you 2 pounds over stock and will set you back a whopping $1547.00! Is the cost worth it? I wouldn't go that far, but it is one of the better muffler systems that I have tried on the 21-22 Honda CRF450R. If I was a Honda owner I would rather invest in a Vortex ECU, have it mapped, and save a few hundred bucks, because the Vortex ECU can do more to help the power character/chassis feel than that of the Akrapovic system. However, if you do have a deep pocket book and are going to get a muffler system anyway, this Akrapovic would be a great choice along with the Vortex. The combo is an amazing feeling once out on the track! It’s a beautiful system and works very well on a wide variety of terrain/tracks. 

Go to akrapovic.com to locate your nearest dealer. 

FMF Fatty/Gnarly Pipe & Powercore 2 Silencer (2022 YZ250)

The 2022 Yamaha YZ250 is a hell of a fun bike to ride. Even though I am not a huge two stroke guy, I had a great time riding it and thought it had a better engine character than the previous model. The new intake design really helps smooth the power down low and makes it broader through the mid range. There is more rear wheel connection than I remember on the 22, which makes four stroke lovers appreciate this two stroke. I had the chance to try an FMF Factory Fatty pipe as well as a Gnarly pipe with a Powercore 2 silencer and wanted to give you some feedback to see if it could be worth your while on your new 22 Yamaha YZ250.

FMF Factory Pipe/Powercore 2 Silencer:

After installing the FMF Factory Fatty Pipe and Powercore 2 there was some noticeable changes to the YZ’s power character. Bottom end had a cleaner feeling down low as the stock YZ250 does feel slightly rich on low rpm situations. As soon as you crack the throttle you will get a cleaner response, but not any added snap down low. Where you feel the Factory Fatty pipe/Powercore 2 combo is through the mid range as the YZ250 has better pulling power when shifting from second to third out of corners. I also had the feeling that the YZ250 now had a longer pulling top end/over-rev feel and could pull 2nd, 3rd and 4h gears longer down straights than the stock system could. When the track is deeply tilled the FMF system does make the YZ250 feel a little more spunky with its clean mid range rpm response so popping out of corners in a hurry is made easier. I did notice slightly less rear wheel traction with the FMF system, but I don’t think people that are looking to purchase a two stroke pipe and silencer aren’t necessarily looking for rear wheel traction. Overall, the FMF Factory Fatty pipe and Powercore 2 silencer is a nice upgrade from the stock system. Not to mention that it looks really nice with that raw pipe against that blue plastic. 

Gnarly Pipe/Powercore 2 Silencer:

If you’re looking for more bottom end hit, lugability as well as more rear wheel traction the Gnarly pipe/Powercore 2 combo is your ticket. This combo will help with bottom end rpm response and keep that clean feel that the Fatty has, but will get you more snap as well as allow you to lug the YZ250 a little more through corners. If you find yourself a gear too high at times through corners the Gnarly has better recovery than the Fatty does. As weird as it sounds this combo gave the YZ250 more rear wheel traction/feel than the stock system or Fatty/Powercore 2. I can roll the throttle on sooner with this set up and not break the rear wheel loose as easy. Mid range meat/pull is slightly better than stock, but not as good as the fatty. The down side to the Gnarly pip/Powercore 2 silencer is that it made the top end feel rich/dirty so I had to lean the clip (raise one) as well as go down one main jet size. Once I did this it helped clean it up but still didn’t pull as good on top as the Fatty did. 

If you have any questions about this test please feel free to email me at kris@keeferinctesting.com.

X-Trig ROCS Tech Triple Clamp (2022 YZ450F)

It’s hard to find aftermarket triple clamps that are better than stock these days, especially on the Yamaha YZ250/450. So much is involved in making a triple clamp that flexes enough, but also has enough rigidity to aid the machine in corners as well. With the triple clamp flex character so important to chassis handling (on all motocross bikes) sometimes it’s tough to find anyone that can make a “comfortable” set of aftermarket triple clamps. Why do you need aftermarket triple clamps? Well sometimes it’s just for looks with some riders, but there are occasions where you might want another offset to help you get more stability or a sharper turning character out of your machine. In this case I was looking for the standard offset for a 2022 KTM Yamaha YZ450F and wanted to see if installing X-Trig’s on the Yamaha hurt or helped it. I was hoping to help cornering positivity without sacrificing rigidity balance. Oh and I also purchased these myself for $850.00! 

Enter X-trig’s ROCS Tech Triple Clamps and PHDS Mounts. “ROCS” stands for “Revolutionary Opposing Clamp System”. The ROCS clamp allows for precise alignment of the fork tube with opposing clamping surface patterns, the stiffness of the steering stem is specifically tuned to the respective motorcycle model, the steering-head bearing is already mounted on the shaft tube for convenience, a special fork slot and clamping area for precise fork operation, precise clamping with special screws for low torque specs, OEM attachments can be mounted without auxiliary material, and flexibility that is adapted to the fork with anodizing in the technical factory OEM look. The difference between the ROCS “Tech” and the ROCS “Pro” is the “Tech” uses a standard offset with a pressed shaft tube. The “Pro” has two offsets you can choose from by simply adjusting the shaft tube (or steering stem). I didn't feel like the Yamaha needed an offset change as the Yamaha is predictable on straight line and corners well, so I stuck with the “Tech” clamps. 

The PHDS (Progressive Handlebar Dampening System) is a system supported by elastomers designed to absorb engine and chassis vibrations. The system also dampens the forces acting on the handlebar in a horizontal and vertical direction, maintaining steering precision. The handlebar can be adjusted in 12 different positions when the PHDS is mounted. The Yamaha doesn’t necessarily vibrate more in the handlebar area than any other 450 motocross bike, so this isn’t something I feel the Yamaha needs particularly, but if it helps, so be it.
Installation of the ROCS clamp is fairly straight forward (with the pressed shaft tube). All you need to do is grease up the steering head bearing and slide the bottom clamp up in the head tube of the frame. Super clean! Mounting up the PHDS bar mounts is a little tricky as the mounts themselves have a lot of moving parts, so make sure to read the instructions to ensure proper mounting. Technical Touch offers optional PHDS bar mount elastomers that come in soft or firm, but I chose to run the stock medium style elastomers, which seem to be just fine for motocross conditions. 

I am super picky about bar positioning, shocking I know and the Yamaha isn't the best rider triangle out there, so I went with the second mounting hole closest to me (when sitting on bike) on the triple clamp with the PHDS mounts back. This handlebar position gave me a +3mm bar position (forward from stock), which I preferred as the stock positioning is a little cramped for my 6’0 frame. The PHDS bar mount itself is +2mm higher than the stock bar mount, which I was just fine with as I am using a SX Race Pro Taper EVO handlebar on the 2022 YZ450F. Having so many positions available for the rider is definitely a huge positive for adjustability with these ROCS clamps on the Yamaha to open up the cockpit for you bigger riders (5’11 and up). If you feel like you need a higher PHDS handlebar mount, X-trig also offers spacers to go under the PHDS mounting system. You can pick from 3mm, 5mm, and 10mm spacers.

So what did the X-trig ROCS Tech Triple Clamp and PHDS handlebar mounts do on the track? My goal for this test was to dissect the anti-vibration qualities as that seems to be the easiest to feel asap. I honestly didn’t notice any less vibration/harmonics through my Pro Taper’s, but I did notice slightly less vibration on higher RPM’s which I found strange. The PHDS mounts do help flex and are a little kinder to my wrists than the stock mounts. While I was looking to get a more precise front end feel through corners, without getting added rigidity on hard pack/rough straights, that is not quite what I found. Basically I got slightly less compliance on lean angle bump absorption so the front tire didn’t exactly feel like it was digging into the dirt enough for me on faster sweepers with chop. The X-Trig ROCS Tech clamp on the Yamaha YZ450F provided enough flex if I was heading straight into bumps, but once I started leaning into braking bumps to set up for the corner, there was definitely less comfort in that area compared to stock. There was some added rigidity when leaning when bumpy and that cause the fork to feel harsher. The ROCS Tech clamp is most noticeable in a positive way when diving deep into a rut where there is a huge load put on the front end, forced by the rider. The chassis positivity through this area is much better than the stock clamps. The stock clamps has a tendency to flex too much and give the rider a wiggle once off throttle in area 1-2 of corners, (on deeply tilled tracks or soft dirt) or give the rider an unsettled (dive) when dropping into a long/deep rut (this sensation can only be felt mostly by faster or heavier riders). The X-trig ROCS Tech clamp gives the front end less wallow (firmer) and more cornering stability once inside the rut (without upsetting chassis balance). Straight line stability isn’t as good as stock as you do feel more of the track under you (front end) on hard pack west coast conditions.

I do feel like slap down landing of the PHDS mounts are more absorbing and I like that feel to my wrists. I am almost keen to try these mounts on the stock clamp to see if that works as good on my old ass wrists! The overall weight of the X-Trig clamp and PHDS mounts are heavier than stock so know that you will be gaining almost a pound of front end weight on your machine. So at the end of the day am i happy with my purchase? I would say for this bike, no I am not. I will say that I have tried X-Trig’s on a KTM with really positive results, but this confirms to me that the average rider DOES NOT need these for his Yamaha YZ450F. Does that mean all aftermarket clamps are rated under the same umbrella? Absolutely not! Not every clamp is created equal. I will try some more aftermarket clamps on this machine in the coming weeks to see if we can keep the stock bump absorption while adding to that positive front tire feel in ruts. Stay tuned! 

Akrapovic Evolution System (2021-2022 KTM 250 SX-F)

When you purchase a 2021 KTM 250 SX-F TLD version the bike comes with a slip on Akrapovic Evolution muffler. However, I know that sometimes, certain machines react better to full systems rather than slip ons, we decided to get the full Evolution system to see how it changes the KTM 250 SX-F’s engine character. 

The Akrapovic Evolution full muffler system has a similar character to the slip on version that comes with the Factory Edition, but with added bottom end roll on and mid range. If you’re expecting a ton of added RPM response (excitement) from your full system compared to your standard slip on, you will be disappointed. You simply will not be getting that much added rpm response with the Akrapovic full system. Instead of a smooth roll on that the TLD version comes with, it now has a little more pulling power in second and third gears and pulls those gears much longer.

Mid range pulling power is increased, but the muffler pitch is so quiet that you never really feel like you’re “on the gas”. The mid range pull is much more linear and longer than the standard slip on or stock muffler and being able to shift a little earlier with the full system makes it easier to ride in softer conditions. I had a hard time with the KTM 250 SX-F at softer tracks not recovering, if I shifted early out of a corner. With the full system at the same track I was able to shift into third and not have to worry about covering the clutch as much. The full system just simply gives me more “meat” in the mid range.
 Top end and over-rev is where this Akrapovic Evolution system shines. Adding top end and over-rev to the already very capable KTM 250 SX-F only makes this machine more fun to ride. Again, I can’t stress on how deceiving this system is because of it’s quiet nature. I really had to focus in and feel how quick I was going from point A to point B on the track because the pitch of the muffler never sounds “racey”. However even with its quiet note, the Akrapovic full system lets the KTM pull so much farther that it almost feels like I swapped to an aftermarket ECU. The connection to the rear wheel with the full system is unmatched and even though it may seem like it’s not very responsive, the KTM with the Akrapovic full system allows the rider to get on the gas sooner through corners. 

As described the Akrapovic badging will eventually get marked off when cleaned.

If you’re reading this and wondering why you can’t simply purchase an Akrapovic headpipe for your Akrapovic slip on, the answer is they will not mate up. The Akrapovic slip on has a smaller diameter OD, (where it meets the stock headpipe), so purchasing just the headpipe will not work. 

A couple of durability notes: 

-The Akrapovic lettering on the headpiece resonance chamber will wear off after a few washes. 

-The Akrapovic muffler stickers will burn away around the 7 hour mark. 

-The overall quality of the system and the parts inside the muffler are second to none. The muffler packing lasts longer than other aftermarket systems and the hardware it comes with is superb. 

-Is the system worth the $1200.00 price tag? Comparing it to other systems out there, I would say you’re getting what you’re paying for. A lighter, race oriented system that gives the rider better overall power throughout the rpm range. 

Dubya Edge Wheel Set

I will be straight up with you all… I am not a huge fan of $1500.00 wheel sets. Most of the time, I am a big stock wheel/hub guy, but in some cases I do need a little more security or toughness  in my wheels. I am a big believer of bringing an extra set of wheels to the track just in case you get a flat or have some sort of wheel failure. Full disclosure: The Dubya Edge Wheel set has been in my shop for more than a year and I am just now getting the information out to you guys now! Why? A couple reasons… I am normally a stock wheel set kind of rider and I am very finicky with rigidity, yet most of the time aftermarket wheel sets have given more rigidity that I wasn’t looking for. Finally, after a year or so, I got off my ass and put them on my 2021 Honda CRF450R as I have experienced some wheel problems with my Honda’s in the past. So why not test the Edge wheel set with a bike that actually could use it! 

The Dubya Edge wheel set was created for the blue collar type of rider that is looking for some added bling with durability. Each Edge wheel set centers around a forged aluminum Edge proprietary hub, which are laced to a Dubya by Excel rim, using stainless steel Dubya spokes and nickel plated steel nipples. Each wheel set is pre-assembled in Dubya USA’s Southern California facility by the same technicians who assemble all of Dubya’s top professional factory riders and teams wheel sets. Instead of using your stock wheel spacers, the Edge wheels come with their own specific spacers to each bike. I actually like when aftermarket wheels come with their own spacers as it can make your dollar stretch further! How? Well, we have a couple Yamahas in the shop that have different axle sizes (two and four stroke) so it’s nice all we need to do is swap spacers instead of getting another hub. It just makes swapping wheels more seamless. 

We have put nearly 50 hours on the wheels themselves and so far we have been pleased. The hub has been surprisingly not as rigid as I initially thought and the rim also has held up to the standard local motocross abuse. I am not over jumping landings or slamming into faces of jumps on purpose, but I feel like I am fairly hard on a bike, yet these Dubya wheels have given me zero headaches. The stainless spokes needed to be adjusted a few times after break in, but since then, they have stayed within a quarter turn of true. For $639.00 I feel like this wheel set is a great purchase for the rider who wants a fresh look on his/her bike as well as some durability that you maybe can’t find at times from your stock wheel set. I also like that the color of the hub doesn’t fade or beed out after several rides/washes. I don’t trust a lot of “inexpensive” wheel sets, but this is one that I am happy to put my hard earned money on. The weight of the complete wheel set is just north of the stock wheel set by a half a pound, but this is something that I did not feel once out on the track. 

The Dubya USA Edge wheels are available with the standard front rim size 21×1.60, while the rear wheels come in 19×1.85, 19×2.15 or 18×2.15 rim sizes. If you’re looking for some cool colors, the rims come in either black or silver, and the hub color matches the brand of machine you’re riding. The only brands that can mix and match the Dubya USA Edge hub colors are KTM (orange) and Husqvarna (blue), since they are exactly the same, but I don’t think you will be running blue on your KTM. Dubya currently doesn’t offer an Edge set up for the #RMaRMy, but hopefully you Suzuki lovers can do your battlecry loud enough, so that John and Kristen from Dubya can hear you.   

If you have any questions about this test please feel free to contact me at kris@keeferinctesting.com 

FMF 4.1 Muffler System (2021 KTM 250 SX-F)

My son and I have been going back and forth on mufflers for his KTM 250 SX-F and have went though about three until we settled on the FMF 4.1. We have tried the HGS (which was good), a Yoshimura, as well as a Pro Circuit system, but for his riding style and what he was looking for from the engine character, we decided on the FMF 4.1 system. Why? Here are some reasons why the FMF 4.1 system works well for Aden and the KTM 250 SX-F. 

First off, the FMF 4.1 system looks beautiful and is easy as pie to put on. Installation literally took 10 minutes and I like that FMF pipe springs last longer than the stock KTM pieces. Aden rides lower in the rpm and only revs his bike in the air (which he thinks helps him but it really doesn’t) so he needs some low end rpm response as well as some low end torque to help get the KTM back into the meat of the power (or “recovery”). You will get more low to mid RPM response as well as more mid range pulling power with the 4.1. Top end is increased slightly plus the over-rev is as good as stock. It is one of the few times that I was impressed with a muffler because it was actually better than stock in almost all areas. THIS IS VERY RARE! Coming out of corners the KTM 250 SX-F now has some more excitement in second gear and pulls harder than the stock system. Third gear roll on is also noticeably more reactive to your throttle hand (increased connection) and can allow for a lazier rider to have more pull in softer loam. We did pull the spark arrestor/insert out with good results and decided to leave it out for maximum throttle response and torque feel. Leaving it in will kill a little low to mid response, yet you still will get better torque feel over stock. 

The downside is that you must keep up on your muffler packing (every 10-12 engine hours) because the FMF will blow out and that could damage your expensive titanium can. Just in case you’re numbers guy, did I mention that you will lose almost two pounds with the titanium 4.1 system? If you slap on spring forks on your KTM, you will be gaining almost three pounds. You can get most of that weight gain with the spring fork back down with a 4.1 Titanium FMF Muffler system.

Things to look out for? I can burn a lot of pants on the headpipe of the FMF system. The magabomb portion of the headpipe can burn your pant just above the boot when sticking your leg out in deep ruts. This has happened on only a couple different brands of gear (FXR, FLY) with the FMF headpipe installed. Overall we are happy with this system for the way Aden likes to ride and will be refurbishing his mufflers every 10-12 hours in order to keep the most performance possible. Hopefully FMF will have these back in stock in the near future so be on the lookout over on their website that gets updated weekly on what is in stock. Damn you Covid!

Slip On Or Full Muffler System (2021 Honda CRF450/250R)

Some muffler questions that get sent to my email inbox usually look like, “which muffler is best for my bike? “Is a full system worth the money or can I just get away with purchasing a slip on”? “Is my stock muffler the best muffler option for me”? Instead of trying to keep answering some of these emails, I thought I would write an article on some of the current 2021 motocross machines and which mufflers do what to the power curve as well as if they are better than stock. Now I haven’t tried every aftermarket muffler out there, but if you’re in the market for one and need to decide on if your bike works best with slip on or full system, you have come to the right place. I have also put together a sidebar on if the stock muffler is worth a crap or maybe you should just save your money because the OEM muffler is a good stock system. Just because it is “stock” doesn’t mean it hasn’t been fully developed by the manufactures. Not all stock mufflers are created equal, so read below and see if you need to keep your stock muffler on your Honda CRF250/450R, get a slip on, or maybe go all out and purchase a full aftermarket muffler system. 

Honda CRF450R: 

Full Muffler Systems Tested: Yoshimura RS-12, FMF 4.1 RCT, Pro Circuit Ti-6.

Yosh Summary: Smoother roll on/less RPM response than stock muffler which makes it slightly easier to control down low. Mid range pulls longer than stock and top end over-rev is as good as stock. 

FMF Summary: Better roll on delivery with a snappier throttle response which can help let the CRF450R roll third gear more through corners. You would think this might be contradictory to what you want out of this machine but this allows to run a higher gear which calms the chassis down. Mid range has a smooth/meaty pull but signs off earlier on top end than the stock system. 

PC Summary: Long linear power character with no real explosive snap down low like the stock system. The PC system calms the Honda’s chassis down under acceleration and adds more mid range, with slightly more top end pulling power. Over-rev is as good as stock. 

Slip Ons Tested: Yoshimura RS-12, FMF 4.1 RCT 

Yosh Summary: Retains more of that smoother roll on power, similar to the full system and keeps the longer than stock mid range power, but to me the rpm response suffered a little on low to mid range areas of the track. I wanted just a little more of that stock muffler excitement in these areas. 

FMF Summary: Throttle response isn’t as good as full FMF system and the Honda will not pull third gear as good out of corners with slip on, but 

Stock Muffler Character: Strong low end pulling power (sometimes too much when rolling corners) with touchy low end rpm response. Broad mid range power with a long top end pulling power. 

Slip On Or Full System?`: The stock muffler is just to touchy down low and that can lead to a lot of mistakes when trying to roll your corners or when you get tired. To me an aftermarket slip on, not a full system is the most bang for the buck on the CRF450R. I prefer the FMF slip on because if it has a snappier rpm response yet a smoother roll on mid range character than stock and this seemed to help the Honda’s chassis the most. The Yosh is also a great choice but maybe slightly too lethargic for my taste on low to mid range rpm response, but I do think t his is a great choice if you’re looking to lighten up your machine as well as tame it down some.  

Honda CRF250R: 

Full Muffler Systems Tested: Yoshimura RS-9, FMF 4.1 RCT, Pro Circuit Ti-6 

Yosh Summary: Less bottom end than stock but more mid range pulling power and top end. Low and mid range rpm response is same as stock with slightly crisper FI feel than stock muffler. 

FMF Summary: More bottom end than stock muffler with increased mid range pulling power, but with less top end pull than stock muffler. Low end rpm response has more snap but muffler is considerably louder than stock. 

PC Summary: Better low end rpm response than stock but with a smoother pulling power out of corners. Mid range pull is longer and allows rider to get into third gear sooner than stock without abusing clutch. 

Slip Ons Tested: Yoshimura RS-9

Yosh Summary: Better low end feeling out of corners than the full Yosh system, but still not as much bottom end than the stock system. Mid range pulling power feels as good as full system but with less top end/over-rev. 

Stock Muffler Character: Smooth roll on delivery with crisp low to mid rpm response. This machine could use more low to mid range torque feel in order to get rider out of soft low speed areas of the track better. 

Slip On Or Full System?: The CRF250R needs more bottom to mid range pull so I have found going to a full system benefits this machine the most. The FMF or PC both have unique characters that I need in order to shift sooner and pull out of corners with more authority. The FMF is a louder muffler system than the PC so if louder mufflers are not your thing you might want to go to the PC system for a deeper/less raspy sound. If you put inserts into the mufflers of the FMF, it kills some of its best benefits (less rpm response/low end feel).  

Akrapovic Evolution Muffler (2021 Yamaha YZ450F)

The Akrapovic Evolution muffler system is one of the most beautiful looking systems out there in the market today, is well built, and has quality welds all the way around it. Once hot, the titanium color of the headpipe is the most dynamic blue you will ever see from any muffler manufacturer, which just makes you feel that much more factory on the starting line right? The Akrapovic Evolution titanium muffler system is 1.5 pounds lighter than the stock YZ450F system and tucks under the right side panel much cleaner than other systems that are on the market. When putting on the system, make sure to leave the headpipe loose and then connect the mid pipe, so that the slip fit joint slides in easily. Once those two pieces are connected, tighten the headpipe bolts and mid pipe bolt just snug. The Akrapovic uses your existing stock heat shields or you can purchase carbon heat shields separately. The Evolution muffler uses an aluminum spacer in the rear hole to give the muffler enough clearance (from the brake caliper) once the suspension is fully collapsed. This system is one of the easiest to install and I have been putting a ton of systems on this blue bike lately. I did notice that there is a small screen deep inside the core of the muffler, however I was told that this isn't a spark arrestor, but a noise insert. Note: Leave the insert in, as the muffler performs better with insert in and is much pleasant to the ear. Once rear section (muffler) was installed, I went around and tightened up the remaining bolts. Doing it this way ensures there is absolutely no binding going on between each slip fit joint. 

Out on the track the Akrapovic Evolution muffler has a deeper sound and is much quieter than the stock system. I started the test with the “TP 3.0 and stock” maps installed inside the 2021 YZ450F (if you don’t know what the TP 3.0 map is, email me at kris@keeferinctesting.com). Roll on power delivery was smoother than stock out of corners (with either map) with the Akrapovic, compared to the stock system. I have grown to love the smoother roll on power that the Evolution system delivers as it really helps me roll my corners better without getting the chassis upset. The connectivity of the Akrapovic muffler is second to none as you will notice more rear wheel connection under heavy throttle. 

The Akrapovic system really comes to life once out of corners as the Yamaha now starts pulling harder and longer than the stock system down straights. Second and third gears can be stretched longer by the rider with the Evolution system and rolling third gear in corners is slightly easier on the rider as well (with stock gearing). Over-rev is better through each gear with the Akrapovic and the overall engine feels like it revs a little quicker/freer. The freer feel takes away some engine braking sensation on de-cel and also helps the Yamaha handle slightly better coming into corners. Yes! All from a muffler! 

In conclusion, I feel the Akrapovic Evolution muffler system is an excellent system once you can dial in your favorite desired Yamaha Power Tuner App setting. You will not be getting more bottom end than a stock system, but the gains through the mid-top end are a noticeable difference. It will be up to you if that difference is worth the $1300.00 you will spend on the Evolution titanium system. Akrapovic’s website is a very informative, clean, and one of the best aftermarket muffler websites to browse around on if you have the time. There are dyno charts, a sound tool that lets you compare the stock system to Akrapovic’s muffler pitch, documents of replaceable parts, and technical data about the system itself. You can head over to akrapovic.com and punch in what bike you want to geek out on. I did, for a while!

Extra Credit: If you’re like me and still want more power yet even more connectivity, look at getting a Vortex ECU mapped by Chad at XPR Motorsports for this 2021 YZ450F. You might think that putting a Vortex on a YZ450F is over kill but what you're getting is a faster, yet easier to ride Yamaha that will allow you to ride it harder. Less on/off feel with this muffler system and the Vortex ECU. I have created a couple maps with Chad on this Vortex and along with this system has made this machine easier to ride. I have let other R&D test riders ride my test bike with these two mods on and they were blown away.

Email me if you have any questions or concerns about this test kris@keeferinctesting.com. 

Dunlop MX12 Rear Tire (120/80-19)

Dunlop offers a wide variety of tires for us moto/off-road guys but you don’t see too many reviews of the MX12 scoop tire out there. I recently had the chance to try a 120/80-19 rear MX12 at a few different tracks that range from sand to intermediate terrain with the occasional hard pack afternoons at Glen Helen. The Dunlop Geomax MX12 rear tire is a soft-terrain tire designed specifically for sand and mud conditions. The Geomax MX12 is the replacement for the MX11 that was out a few years ago. The Geomax MX12 rear tire was made to try and improve performance in mud, sand and soft dirt while expanding the range of conditions it can be used compared to the older MX11 design. Dunlop designed the MX12 to have increased rear wheel acceleration traction, lean angle grip, improved control in ruts and enhanced bump absorption when coming into corners. 

Fresh Dunlop MX12

With Dunlop’s V-block tread pattern and over 1.5 inches between each row of knobs, the MX12 is can scoop dirt and help move the motorcycle forward in places where a standard MX33 tire would need more help. Additionally, the V-block pattern helps fling mud off of the tire and cleans it off in wet conditions. Dunlop’s block-in-a-block progressive cornering knob technology, used on the MX33 and MX53 tires, has been implemented on the MX12 as well to help cornering traction and slide control. Ribs have been added to the backside of the knobs to improve stability in braking and choppy rutted out corners. No matter how much traction you get out of a tire, it will never be good without consistency. Without these ribs, the steep knobs could bend and fold over, which you don’t want when trying to get on the throttle hard (while leaning) out of a corner. In the testing world, we call this “cornering stability”.

I have ridden with a Dunlop MX12 on 250 and 350’s before but this was the first time I have experienced it on a 450. It’s seriously like cheating when coming out of softer corners. Getting on the throttle harder is made easier as the motorcycle accelerates harder with less throttle. This also makes abusing the clutch much less and allows the rider to use less energy around the track. Another notable positive for me was being able to use alternate softer lines that were too deep for previously used soft to intermediate tires. Instead of sinking into soft soil, the MX12 tire stayed on top of the dirt much better than other soft-intermediate tires. When compared to the Dunlop MX11, the MX12 is easier to lean into a corner and maintain that lean in a choppy rut. Cornering stability has improved on the MX12 (compared to the MX11) and it’s also easier to keep that lean in a rut that is choppy and hacked up.

Dunlop MX12 With 6 Engine Hours Of Soft To Intermediate Terrain Time

The portion of the test where I was most impressed though was how the MX12 reacted to harder conditions. On intermediate to hard terrain, the MX12 dug into the dirt and hooked up surprisingly well. With the added stability from the reinforcing ribs and the staggered knob pattern, the MX12 felt better than some other intermediate to hard terrain tires I have ran lately. The downside to the MX12 was that on hard pack flat corners it doesn’t have the best lean angle grip. It will slide around more than I would like, but that is to be expected on hard pack with a scoop. However, if there was only a couple parts of the track that had hard pack corners (and the rest of the track was softer), I would gladly take this MX12 because that is how good it works on the other parts of the track. The durability of the MX12 is great if used on strictly soft terrain, but if used on intermediate terrain it can break down the carcass of the tire much quicker. The knobs will not chunk as quick as the carcass will break down. The ribs in-between the knobs will break down over time faster on hard pack. A starting point that I liked for air pressure was anywhere between 12-12.5 PSI.

Dunlop MX12 With 8.6 Engine Hours Of Soft To Intermediate Terrain Time

If you are looking to get great starts on softer conditions and hook up out of corners like you never have before, look at the MX12 scoop tire. This tire has changed my way of thinking when it comes to what I am going to be running on race day. I wouldn’t even mind running it on late afternoon motos at Glen Helen. Just because of the scoop design, don’t disregard this tire when the conditions go from soft to intermediate. This MX12 rear tire still hooks up well! You can find the MX12 over on rockymountainatvmc.com for $93.00.

Yoshimura RS-12 Stainless Muffler System (2021 Kawasaki KX450)

The stock 2021 Kawasaki KX450 is pretty damn good machine, but that muffler looks atrocious right? We called up on Yoshimura to see if we can get a more attractive aftermarket muffler system that is actually better than the stock system. I will say that the stock KX450 muffler system works pretty damn well, but as always we are constantly looking to try aftermarket pieces because as we all know, you are only as good as what you try! 

The Yoshimura RS-12 Stainless System is made in the USA, is rubber mounted to the subframe, its asymmetrical shaped muffler allows maximum capacity and incorporates a resonance chamber for managing sound and increasing usable power, the unique shape also provides more clearance for tire and brake caliper, has a new patent pending Precision Taper Fit (PTF) insert ring that can make it easy for the consumer to install and remove sound inserts as well as spark arresters, comes with a carbon fiber end cap and can be fully rebuilt with repacking kits that Yoshimura sells. If you’re looking to lose a little weight with the muffler, you will have to look towards the titanium system. The stainless system weighs in at 9.12 pounds, which is slightly heavier than the stock muffler, that comes in at 9.1 pounds. We aren’t necessarily looking to lose weight in this instance, as power, sound and reliability are more important to us with this unit. 

The stock muffler system is pretty damn good, as the power character of the KX450 is long and linear, but the stock KX450’s engine character could use a little more pulling power and more mid rpm response. Installing the Yosh RS-12 was painless enough and we really appreciated the rubber sub-frame mount that the Yosh muffler comes with. Having a rubber mounted rear muffler mount helps avoid the sub frame tab breaking off due to solid mounting. Once on the RS-12 is visually still big looking, but the RS-12’s exhaust note is so much better to the ears that we lost focus on how big the RS-12 looks. Out on the track we noticed how much easier the KX was to corners because there was less on/off feel from the engine on low RPM because the Yosh builds power a little more smoothly between 5000-7000 RPM. The RS-12 is less touchy to the riders throttle hand and to me that helped calm the chassis down in area 2-3 of corners. You will not get as much throttle response from the RS-12 as you do a FMF or a stock system, but to me this is a good thing. The mid range pulling power is what you will come to love from the Yosh system. Pulling power out of corners is noticeably better than stock and the rider can shift into third earlier without having to use the clutch in order to get the engine to recover (back into the meat of the power). Rear wheel traction was also an improvement on hard pack tracks as the KX450 had a better second gear flat corner sensation to the rear wheel than the stock system. Top end feels as good as stock with maybe a little more over-rev, so if you’re a little lazy the RS-12 can help you slightly in that area as well. 

If you’re looking for a more explosive rpm response from your KX450, the RS-12 may not be the muffler you want to go with, but if you want added pulling power out of corners as well as more rear wheel traction with a better exhaust note, then this Yoshimura RS-12 stainless system for your KX450 is a great buy. The benefit about stainless steel is that the overall construction of the muffler will last longer than titanium. Most of my practice bikes over time had stainless systems on it for the sake of durability. Slip fit titanium joints just don’t last as long as stainless. For $850.00, the RS-12 system is a good buy with quality construction that you expect from Yoshimura.  

FMF 4.1 RCT Muffler System (2020-2021 Honda CRF250R)

The 2020-2021 Honda CRF250R chassis is one of the most fun to ride in the 250 class, with its easy to corner nature as well as a great suspension package. However, Honda focused a lot of their engine R&D on peak horsepower and not torque, which to me the CRF250R lacks the most of. When riding the Honda back to back with other models in its class, it’s obvious that the Honda needs a little help/pulling power out of corners. I went to FMF to see if they had what I needed in a muffler package and came away with these thoughts for you to digest. 

Let’s address the elephant in the room first. Can I even get one at this time? Sadly, most likely not. COVID has done a number on a bunch of stock with anything related to dirt bikes! This is not just with FMF, Pro Circuit, Yoshimura, etc., as this is happening with a lot of other key parts to our industry as well. The reasons go from not enough workers/employees to keep up with the demand to not enough material to build the product. This pandemic affects eery business and our industry is no different. This is a good thing and bad thing. Our industry seems to be booming, which is great, but us die hard moto dudes have to wait for months to get a damn muffler! That sucks and I get, but you need to breathe! FMF plans to have Honda mufflers back in stock in March, so if you have placed an order for one of these or any other Honda FMF muffler system for that matter, look towards the middle of March for delivery. Give these muffler companies some time and patience as we all are dealing with some sort of back log because of the pandemic. Plus I have heard that some people just simply don’t want to work at this time!

I like the fact that even though there are two headpipes and two mufflers it still didn’t take that long to install. The headpipes go on super easy and the mufflers slide into the slip fit joints with ease, yet are tight enough so the joints don’t wear out too soon. I have over 20 hours on the FMF 4.1 RCT mufflers and the slip fit joints are great, which is rare for titanium slip fit joints. Another added feature is that you will be losing close to two pounds off of your CRF250, which can also aid in helping the Honda’s chassis even more.

So let’s start off with a couple things I didn’t like from the FMF 4.1 RCT system. The pitch/sound of the FMF 4.1 RCT mufflers are LOUD! The sound is deep and throaty but it is loud compared to other aftermarket mufflers! I didn’t run the quiet inserts, but I plan on trying these to see what it does to power and sound. Once I rode with the system for an hour or so the sound actually improved/dampened as the packing inside expanded. So don’t completely freak out when you first start it up. The second thing that you must pay attention to is that the headpipe springs can break and that could cause your headpipes to pop away from the exhaust ports of the cylinder head. I had this happen two times over the course of almost 22 hours so make sure you keep new springs on the headpipes. I learned if you keep new springs on, the headpipes remain on and don’t give you any issues. I would go no more than 8-10 hours on a set of pipe springs. 

Now with everything I did like about this muffler system: The power delivery is great and FMF made more power where the CRF250R needed it! The Honda needs bottom end and this is the only dual muffler system that has given me more grunt/low end out of corners! THANK YOU! The Honda CRF250R comes out of ruts/deep soil stronger and pulls harder through the mid range. Second and third gear recovery is improved as well as low-mid RPM response. The FMF 4.1 RCT muffler system makes the Honda feel more exciting and lighter around the track, which helped me improve my cornering. Top end/over-rev is as good as the stock mufflers and to me that is just fine because now I am able to short shift the CRF250R more than I could with the stock system. I am running a 13/49 gearing spec with the FMF 4.1 RCT system and that gives me more options with third gear through corners. With the stock muffler and 13/48 gearing, using third gear wasn’t even a thought in my head.

The FMF system will set you back $1500.00 which is my last gripe of this article! Holy crap that is expensive, but at least I know if I have my mind made up on spending my money on an aftermarket muffler system, I know I am getting something out of it with the power increase.  You can visit rockymountainatvmc.com or fmfracing.com to get yourself on the list for the next production run. 

HGS Exhaust System For 2021 KTM 250 SX-F

Something that most riders (including me) may not see a lot of in the states is HGS exhaust systems. HGS is a Netherlands based company that has been making exhausts since the early 90s and are mostly popular among European club riders and of course many factory supported MXGP teams. I had the chance to try out an HGS exhaust with the Conical silencer on a 2021 KTM 250 SX-F supplied by Bud Racing (American porter for HGS) and wanted to get you all some feedback on a muffler system you may have never heard of.

The stock engine character of the 2021 KTM 250 SX-F has a smooth roll on power delivery that comes on strong through the mid to top end range. The over-rev of the KTM 250 SX-F is down right impressive and allows the rider to stretch each gear farther than any other 250 MX machine out there. Other mufflers I have tested provided great mid-top end gains but it was very difficult to get more low end. I was looking to get some more low-mid range gains from the HGS and that is exactly what I got. First things first though, how was the HGS to put on? I am not going to lie, it wasn’t the easiest system to bolt on! The headpipe fitment to the cylinder head was very tight and took some coaxing to slide into the exhaust flange. Once I finally got that slipped over and fit up the rest of the system bolted on without issue. I am not going to look forward to taking this system off as I know that headpipe will be a tough one to get out even with the generous amounts of anti-seize I put on around the lip of the HP. 

The weight of the HGS is not one if it’s strong points as the complete stainless system weighs only 11 ounces less than the stock system so if you’re looking to lose more than a pound on your KTM 250 SX-F, you might want to look elsewhere. However, most consumers that purchase a stainless system expect to have some weight along with it and pick up durability instead right? In this case that is what I was looking for because this system was going to stay on my son’s practice bike for a while and get beat up.

Like I mentioned above ,out on the track the HGS system has more bottom end pulling power and really pulls much harder than the stock exhaust through the mid range. Accelerating out of corners in second gear provides more recovery/pick up than the stock muffler and allows the rider to shift to third gear sooner than the stock system. I like that the HGS system gives the KTM a little more low end RPM response and makes the KTM feel even more playful in low speed/RPM situations. When the track is tilled deep the KTM 250 SX-F gets on top of the soft stuff better with the HGS system and each gear can be stretched out just as long as the stock system. You will not be getting any more top end/over-rev with the HGS, but for what my needs were for this bike, that didn’t matter. The overall look of the muffler isn't that appealing but I am the type of guy that is looking for function over fashion when it comes to my parts on my bike so I give this muffler a pass because it worked so damn good on the track.  

The exhaust note is pleasant and not too loud and has a similar stock sound to it. My B level son even mentioned how he liked how good the KTM 250 SX-F now felt coming out of corners and to my naked eye that was visible as well, as I was watching him. Now comes the tricky part… How do you get one? You will have to go to Bud Racing website www.Budracing-usa.com or call them at 951-245-2660. The cost of the HGS system with the Conical silencer is $849.99 and from what I have seen, they have them in stock! That’s right! IN STOCK! Something you may have not heard of since this pandemic hit.

Any questions about this system please email me at kris@keeferinctesting.com. 

The Makings Of A Great WP Pro Component Settings On The KTM 450 SX-F (With REP Suspension)

Let me preface this article with how much I like to ride the KTM 450 SX-F. But… Yes, of course there is always a “but”, right? I like a lot of things about the KTM 450 SX-F, but the stock suspension isn’t one of them. The AER fork is a slight headache for me as it’s stiff as hell when new, then once broke in, moves more in the stroke, yet still gives a harsh mid stroke feel on braking bumps. Not as much as in year’s past, but it still isn’t a spring feel. Raising the air pressure only makes the harshness worse and decreasing air pressure allows the fork to ride too low in the stroke for my taste. I am a front end steering rider and that means that I really like a spring fork feel. Now, I have tried some other companies spring conversions and although better than the AER fork with front end traction/feel, I just wasn’t sold on the performance it gave me on rough tracks. After doing some of these tests, I then resorted to a WP Cone Valve fork. Now I am not going to sit here and tell you that slapping on a set of WP Pro Components is the answer to your front end problems, as I did have to go through several setting changes in order to get a feel that I personally liked. I thought why not walk you through some of the process to create settings as well as tell you about the latest one I have on our 2021 KTM 450 SX-F test machine. 

You know who helped me get to this blend of KTM comfort and performance promise land that I am in? Mark Johnson at REP Suspension. I am a serious pain in the ass when it comes to KTM suspension, probably because I love that damn Yamaha KYB/SSS fork so much (yes, I know there are KYB conversions and we are going to test one soon, don’t yell at me). Although Mark made my WP Pro Components better than my stock stuff the first time he did it, I felt like I wanted more comfort on rough tracks. I complained to Mark that my rear end always felt too low under acceleration and the front end still had a firm feel on slap down hits through my handlebars. I complained. He listened. That is what great suspension tuners do. They listen to the customer. There are several companies like this out there and REP is one of those companies. Mark emailed me one night about a setting he came up with, that he thought I might rather enjoy. I honestly thought what I had was decent, but as one old test rider once told me, “you’re only as good as what you try right” and I am in the business to try and relay that back to you all right? So I immediately got excited about another suspension test that could really be “THE ONE”! 

I met Mark at GH one Thursday and we literally stayed there all day. This is nothing new, but as a guy who has been doing this 20 or so years, I still love it! I wanted to make sure that I left GH near dark and when the sun decided to set behind the hills of Glen Helen, I wanted to make sure that I had comfort along with performance, before I gathered my things and left. This is the only way I can sit here and type to you all and say if it’s better or not. When you move from a stock WP AER fork to a WP Pro Component set up you will immediately feel a heavier turn in, yet will receive more front end traction. It’s a give and take and I will gladly take a heavier steer in (area 1 of the corner) for added traction. I don’t have near as much of a problem with the rear of the bike, but the stock shock, once hot, fades away into oblivion and gives no real damping character at the end of a longer/rough Moto. I wanted consistency, comfort and traction. Is that so much to ask from a bike? The Kawasaki gives it to me. The Yamaha gives it to me. I want the KTM to give to me as well with WP components on it! 

As usual I make sure that each test is a blind test. I make damn sure I know nothing about what Mark and the REP crew do to each setting and that I am going strictly off of feel when riding. I make sure I hit the same lines on the track through out the day for consistency and that ensures proper feedback to the REP crew (as well as you the reader). When all was said and done, what REP gave me was the best setting I have ever felt from any KTM set of suspension I have tried. Oh and I have tried a lot. Is it the best suspension that I have ever met period? No, but it was the best KTM stuff I have tried, hands down. I was starting to consider that the WP Pro Components were just built for performance and not comfort, but Mark and the guys proved to me otherwise.

 The WP fork with the REP setting not only had hold up, but had comfort as well. Most of the time when you go to an A-Kit style fork, you will lose comfort and gain performance, but both of those categories went up equally for me. RARE! This has only happened twice in my time of testing! Using a 4.8 N/mm spring rate along with the parts listed below gave me great lean angle traction (off or on throttle). The downside to my previous CV fork setting was that if I loaded the front tire on lean (under throttle) the fork deflected and felt harsh. The new updated setting felt more supple initially and progressively had more damping feel as the fork went down. There was no unexpected stiff shelfs in the travel as the fork moved and in return, that gives the rider better feel to the front wheel/tire. AKA more tire contact patch! Boom! Gone is the harsh slap down feel to my hands and that increased my ability to be more confident in how hard I can push into/through jumps because I know that if I wanted to overjump a section (on purpose or maybe by mistake) I could do it without an issue. 

The WP Pro Component shock has always been a struggle for me to set up. I always felt like my rear end was too low and when I managed to get the rear end up, it was god awful coming out of corners (harsh and wasn’t fun on my back). Although I gained consistent damping feel over a longer Moto with the Pro Component shock the comfort was difficult to find at times. To help this I ran REP’s knuckle without the longer rods, along with a sag setting of 98mm. I wanted to change the curve of the linkage ratio to help acceleration comfort, but try to keep that rear end up under throttle. This did get me slightly more comfort, but felt like it pushed on the front end too much once transitioning off the throttle. Mark suggested that I try a 1mm longer shock shaft and that really changed the character of this bike. Once I had the chance to ride with that, it altered my outlook on how the KTM’s ride attitude could handle rougher style tracks. The rear end stayed up higher in the stroke and for my 5’11 front end steering frame, this was a game changer. The KTM became more balanced on throttle and allowed me to accelerate harder/sooner out of choppy corners. I now could get my sag numbers back to normal range (103-105mm), which left me with a balanced feeling coming into corners (off throttle). Having this 1mm longer shock shaft also allowed me to run REP’s longer pull rods, which increased rear wheel traction and took some bite/harshness out of any initial braking bump hit. 

Now on to the question that I will get asked after this is published… Keefer, I just spent 11K on my KTM and now you are saying to purchase 5K on suspension  as well as put another 800.00 into those Pro Components? Holy shit! Yeah, I know, right? However, it’s crazy how many people actually do this. So to cater to those people as well as to others, I will also be doing a stock re-valve story just like this one coming in the next few weeks. So hold tight! Not everyone has the money for Pro Components and I am not blind to that fact. I really wanted to get this article up because I had my doubts about these WP Pro Components at times and get tons of emails about them. Mark and the REP crew worked their asses off to make me happy and it took me a while to get there, but hopefully with all of my testing that I have done, as well as REP’s work, you all will benefit from a one and done setting! 

Below are the parts that REP incorporated into my WP Pro Components and what each part’s purpose really is: 

  Fork:

1. Cone Spring Perch System $349.99

Gives more bottoming resistance/progression allowing for a softer more plush setting to be utilized for better top of the stroke feel without losing bottoming. (The concept comes from KYB which I have played with a lot).

2. Low Speed Valves $120.00

Allows us to valve the flow of the needle and is fully tunable to each rider. Riders typically comment less front dip/more controlled front under braking.

3. 13 Degree cones $160.00

WP only makes 3 degree options 15, 11 and 8. Mark makes 13 as well for MX/Off-Road and 8 for SX. This helps bridge the gap between the degrees to get a specific damping the rider is looking for.

4. Low Friction O-Ring Kit $11.99

Lower cartridge friction compared to the standard o-rings that come in the fork.

Shock:

1. Trax LSV $250

Similar to the fork LSV, it gives REP another shim stack to play with, that normally is not in the shock. The shim stack controls the needle flow and is fully tunable. (This is the part that I felt gave firmness without taking away comfort). It also majorly decreases hysteresis, or pressure differentials, in the shock, which results in a more consistent feel and performance in the shock. 

2. Shock Spring Thrust Bearing $62.99

Springs naturally want to turn as they are compressed which causes binding. The bearing is fitted on top of the spring to allow it to turn and can be put on without the damper being disassembled.

3. RCU Spacer $21.99

REP has spacers made that go on both sides of the shim stack that are surfaced ground to be more flat than production. The spacer makes for a more consistent and predictable build as far as dyno and rider feel is concerned.

4. 1mm Longer Shock Setup $112.99

Helps balance of the bike for most riders, but also gains comfort as it puts the linkage into a softer part of the stroke.

Chassis:

1. REP MW1 Knuckle $299.99

Price jumped from up from the last write up I did because they now build them with OEM Bearings and seals.

2. 149mm Pull Rod $219.00

It’s longer compared to the standard 148.2mm for the flatter leverage curve Mark was looking for, also built with OEM bearings and seals.

DR.D Stainless Full Muffler System

By: Michael Allen And Kris Keefer

It’s no secret that Doug Dubach knows Yamahas. That being said, after years of testing for Yamaha Doug started Dubach Racing Development where he builds finely tuned exhaust systems for other major motocross models. However, this isn’t one of those “other” motorcycles and we wanted to take that atrocious sounding stock muffler and try something we haven’t tried.  I met Doug through Kris and have had the privilege of hearing some old testing stories, listening to him give Kris shit, giving me the basic inner workings of exhausts and testing in general explained to me. I really look up to Doug and Kris’s testing abilities both, so when they sent me a DR.D system to try on the 2021 YZ 250F, I was excited and nervous at the same time. Excited because if anyone knows how to make a Yamaha work well its Doug. Nervous because I knew the exhaust wasn’t the only thing being evaluated; Kris always expects me to go into any test with no pre conceived notions about the product and he’s always evaluating my ability to test which is a bit nerve racking.

It’s no secret that the Yamaha YZ 250F has a damn good production engine. When the bike was redesigned in 2019, the power characteristics of the engine slightly changed from making the majority of its power lower in the RPM range, to slightly shifting the peak power up in the RPM range giving the bike a lighter, free revving feeling. While this more playful feeling is fun to use, there was still a part of me that missed the low-end grunt of the previous engine character. After Randy Richardson gave the bike a proper break-in at the Dubya USA World Vet Nationals, the stock muffler packing was extremely blown out, there was seemingly no packing left in the can. I love doing back to back testing because the difference in performance (good or bad) of a product will be far more obvious if the comparison is made the same day. So when at Glen Helen racing the Swap Moto Series I decided to race the first moto with the blown out stock muffler, and the second moto with the DR. D system. 

Although some people may think that since the exhaust wraps around the engine it must be a pain to change it was very straight forward. There was only one step that I found I needed help with to make the process easier, which involved my wife, her butt and me asking for her to sit on it….. With the stock system removed, I simply needed my wife to sit on the bike so that the shock would compress and move back enough in order to get the head pipe between the frame, shock and engine. One other tip is to tighten the two exhaust stud bolts before installing the muffler because leaving the muffler off allows for more room for a wrench. Aside from that step, leave all the bolts finger tight until all the parts are installed, so that there is a little wiggle room. 

After racing moto one I’m sure most of the spectators ears were pleased when I rolled up for the second moto with a fresh exhaust. The first thing I noticed was the change in the exhaust note, gone was the raspy clapped out tone that bellowed from the rear end of the 2021 machine. That raspyness had been replaced by a more throaty sound that obviously had more backpressure and sounded crisp. As the man in overalls ran back to the doghouse to drop the gate I focused solely on my technique and to my surprise when the gate fell I instantly felt far more connectivity from my throttle hand to the rear wheel. I got a great jump, and stayed right with the KTM 350 that was next to me until about half way through third gear. It doesn’t matter what exhaust you have, nothing is going to make up for 100ccs, not to mention all the 450 machines in my class. In addition to the improved connectivity, the power with the new system has been smoothed out. Don’t let that be confused with mellowed out; in fact the DR.D system has noticeably more mid to top end over stock, yet also gave me a little more low end that I wanted back from the Yamaha. Instead of just making noise and spinning, the bike is now able to put that power to the ground and drive forward. The DR.D system not only helps get the power to the ground, it helps clean up some of the FI setting near the low end range on slower corners. I felt like the NS-4 muffler brought some added mid range meat to third gear and allowed me to make my shifting points later than the stock system did. 

To be honest, most manufacturers in 2021 make very good stock exhaust systems that don’t leave much room for improvement. When it comes to performance gains over the blown out stock system, this DR.D full system surprised the hell out of me and I think an exhaust shootout may be in order soon. With a price tag of $659.95 this stainless and aluminum system is a great deal when compared to the price of other manufacturers and is still lighter than stock by over a pound. It may not be the lightest thing on the market, but let’s get real, you and I don’t need the weight loss on our machines. Maybe I need to lose a few before my machine. Once again Doug proved that during all those years helping develop Yamaha’s YZ’s he was taking notes on what works and what doesn’t. If you have any questions about the 2021 YZ 250F DR.D exhaust system, reach out to me at Michael@keeferinctesting.com.

You can get a DR.D muffler system over at www.dubachracing.com.

Keefer’s Notes: 

 I concur on what Michael has written and would like to add that to me the bottom end character is improved with the DR.D on. The bottom to mid RPM response is not only better but to me gives the rider more control around the track. Michael mentioned being more connected to the rear wheel and that right there is what I noticed the most. 

Zero Resistance Throttle

I am one to usually change my throttle tube out several times during the lifespan of my test machines. Plastic tubes wear out and it can get tough to pull the throttle after some use. I am not a huge fan of aluminum throttle tubes because they help throttle resistance minimally and usually give me a more rigid feeling through the right side of my bars. Yes, I am sensitive to rigidity and no not everyone will feel more rigidity when going to aluminum throttle tubes. I’ve had a ZRT Throttle in my possession for quite sometime, but have been hesitant to try it for a couple of reasons. Full disclosure, I dragged my ass on this test because you’re required to cut your handlebar down 1/2 inch on throttle side to compensate for the bearing and I am picky SOB when it comes to bars and like I mentioned previously it was an aluminum tube. I put my ego to the side and strapped on my clear minded testing brain and came away with these thoughts: 

How does it work? Simply put, there are two radial ball bearings on each end of the tube. One located inside the throttle housing and one on the end of the handlebars. This gives the throttle assembly an ultra smooth action and a claimed longer lifespan. Unlike traditional plastic throttle tubes, the weight of the rider either pushing or pulling on the throttle will create some type of “friction”. The longer this goes on, the more the throttle and handle bars deteriorate and I have seen the right side of my bars look like slot car tracks in the past. Inserting two bearings within the throttle tube helps eliminate wear and friction, making your throttle assembly ultra smooth.

So does it work? Yes, it does and sometimes too well! What I mean by “too well” is that it works so good that sometimes I get whiskey throttle when I get tired or have massive arm pump. This throttle is so smooth that it can be easy to grab a handful when sometimes you weren’t expecting to. However, once I got used to the buttery twist, my whiskey became less and less. This is by far the biggest difference I have felt from an aftermarket throttle tube. The fears I had of cutting my bars and getting a different feel quickly went away when I rode out on the track. The 1/2 inch of bar loss was made up by the ZRT and my 802mm of bar width remained the same. Oh and trust me, if it didn’t feel the same, I would have felt it. Now when I go back to other test bikes that don’t have the ZRT tube on, it feels stiffer and harder to pull. We have been running the ZRT tube on our Husqvarna FC450 machine for almost 30 hours and have done nothing to it. I like that it feels as good as when we put it on and we have done zero maintenance to it.  

Of course there is a downside and the downside is that it costs $179.95! Now to most this is outrageous right? But to some, this costly part is worth it. For example, I would want a ZRT if I owned a KTM/Husqvarna/Gas Gas. Why? I am not a lock on grip guy, so I would normally go straight to an aftermarket throttle tube and instead of purchasing a cheaper plastic tube or an aluminum throttle, I would spend the money to get the ZRT. If you plan on keeping your bike for a few years or even if you get a new bike every year (albeit the same brand) this throttle tube is worth the cost. You can order your Zero Resistance Throttle at zrtthrottle.com. Any questions email me at kris@keeferinctesting.com

Ride Engineering Split Triple Clamps (KTM/Husqvarna)

The stock KTM/Husqvarna clamps are too stiff for me! What about you? Well, if you’re here reading this, chances are they might be too rigid for you as well!  It’s odd because most other manufacturers OEM clamps are on the soft side, but the Austrians had something more rigid in mind when making these stock clamps. So in search of other options besides an X-Trig ROCS or a KTM Factory Edition clamp, I went out and tried Ride Engineering’s new split clamp. When Ride Engineering set out to build the KTM clamps, they’ve been designed with four goals in mind: 1) Optimize body position: (Bar position 3mm back from stock). Ride Engineering also offers optional offset for their bar mounts providing 4 bar positions as measured from the stem hole: 6mm forward, 9mm forward, 15mm forward & 18mm forward (using stock bar mounts your positions are either 7mm or 17mm forward); 2) Flex: this new split design made from 2024 aluminum is said to provide better comfort; 3) Improve the handling with a new gull wing design; 4) Place the upper pinch bolts in the front and allows for different aftermarket handguard mounts. Each set comes with a frame mounted hour meter relocation bracket so that you can retain your OEM hour meter. So how did they perform on the track? We break it down for you here. 

The stock KTM triple clamps are stiff natured and can make your orange bike feel rigid/harsh. My goal for this test was to find less front end vibration through the bars, more front end comfort, as well as try to get a more precise front end feel through corners, without getting added rigidity on hard pack/rough straights. Basically get a more compliant KTM 450 SX-F, but that is sometimes tough to do right? The good news is that this is exactly what I found with the Ride Engineering Split Clamps. The Ride Engineering clamp on the KTM 450 SX-F provided enough flex on small bumps, which gave me less of a stiff feel through the bars, yet was also stiff enough to give me a positive front wheel lean angle through flat corners. The Ride Engineering clamp is most noticeable when diving deep into a rut where there is a huge load put on the front end, forced by the rider. The chassis positivity through this area is much better than the stock clamps. The stock clamps have a tendency to give the rider a rigid feel when weighting the front end (although slightly more positive feeling), deflection on de-cel bumps and vibration that is not very friendly. The Ride Engineering clamp gives the front end more tire contact patch feel because it allows the front end to absorb more of what the track is offering the rider. Going firmer on the triple clamp can give a rider more positivity at times, when leaning into a corner, but in this case, I felt like I could get into a corner much easier with the Ride clamps. Straight line stability is improved because of the bump absorption character of the Ride clamp and vibration is also down which gives the bike a tighter, less clapped out feel. Also do yourself a favor and get rid of those stock Neken handlebars. Buy some Pro Taper EVO bars and thank me later!

Compared to a factory KTM clamp (that comes on the Factory Edition) the Ride Engineering clamp does have a little more flex to it than the KTM FE clamp. The two share the same split design, but offer different flex characters on the track. The KTM FE clamp does have a slightly firmer feel, which does help area 2 of corners when pushing your front tire/front end hard while banking off of ruts. The KTM FE clamp does give a little more positivity in that area, but in all other areas of the track the Ride Engineering split clamp just has more comfort.  I tried the Ride Engineering Split Clamps with the stock mounts and the rider triangle of the bar mount position on the clamp wasn’t an issue for my 6’0 frame. I also have tried the Ride Engineering bar mounts, so if you’re taller and looking for more room, you might want to look into a set of the two piece bar mounts from Ride as well.

A lot of back to back testing went down against the KTM Factory Edition clamps in order to figure out how much flex was too much or too little.

Ride Engineering offers two offsets (22mm and 20.5mm), comes in four colors (black, orange, silver, LE blue) and redesigned with a 90mm span to accept the stock bar mounts and mounting hardware. The $689.90 price tag is also not as steep as some of the other clamps in its class and to me Ride Engineering is one of the few aftermarket chassis part companies that actually test their own products. To have an owner that rides his own parts, then makes an educated decision on if it’s better than stock, is pretty damn cool. You can check the Ride Engineering Split Clamps out at ride-engineering.com. 

If you have any questions about these clamps, or any others for that matter, or maybe want a discount code, hit me up at kris@keeferinctesting.com. 

Hinson Momentum Steel Clutch Basket

Hinson makes steel clutch baskets that replace the aluminum standard baskets on Honda, Yamaha, Suzuki and Kawasaki MX machines. If you’re wondering what the benefits are, let me tell you how I stumbled across this basket years ago. I was looking to smooth out the hit of one of the first generation YZ450F’s and there weren’t any flywheel weights available, but Hinson was offering a heavier steel clutch basket. Fast forward to 2021 and I have found it tough to find a slightly heavier flywheel for the YZ450F so guess what? I thought I would revisit this and see how it works in my 2021 YZ450F test machine. First the steel adds durability and strength to a part that wears, often the aluminum of the basket’s fingers develop grooves where the drive plates press on them. Over time this makes the clutch action poor and increases slop in the drive of the bike. The end result is often broken baskets and even worse, broken cases as the clutch basket comes apart.

Secondly, the added weight adds rotational inertia inside the engine helping to keep the rear wheel from spinning and also smooth the pick-up of acceleration as you increase the throttle. Since the spinning ratio is reduced compared to the crank, the weight effect is slightly less pronounced than a flywheel weight, but still can offer benefits from what I have experienced on our 2021 YZ450F. 

A flywheel weight on certain bikes can calm the power delivery. In some cases, heavy flywheels can smooth low end power and just replace the point of power that is now smoother, somewhere else in the power range. That is NOT always great! I am fairly picky about the engine delivery of a big 450, so as much as I love a Yamaha YZ450F, I wanted to smooth out the power coming out of area three of corners, in order for the rear wheel to hook up more. I have been having a problem wheeling the YZ450F when under the throttle hard as well as getting wheel spin out of corners when accelerating to clear jumps. I can’t seem to tune this out with the YZ Power Tuner, so here we are…  

Enter the Hinson steel clutch basket. Depending on the application it can be up to two pounds heavier than the stock basket. Made from precision machined steel, it is impervious to wear on the ears, like the standard aluminum baskets can be. To install the Hinson steel basket you do have to remove your standard clutch basket, so just be forewarned this process can take a while. You then must drill out the rivets and replace the drive gear on from the back of the stock clutch and install it on the Hinson basket. (Some kits come with a new kickstarter gear and drive cushions as well.) Hinson recommends using their cushions (which come with the basket), especially if your bike has some time on it. This install process takes slightly above normal mechanical know-how and tools, but it isn’t much more than a 90 minute job with the included step-by-step instructions.

Right from the get go I am able to feel the Hinson steel basket’s effect on the engine character of the YZ450F. It doesn't seem to affect the throttle response much at all, but it does smooth the power out when accelerating out of rut. I don’t know if this mod is something that you east coast/soft dirt riders would necessarily need, but if you ride loamy to hard pack dirt this is something that can help forward rear wheel bite. The YZ450F has a stock engine character that spools up quicker than other 450’s in its class. With that being said, that kind of power can be really good for soft dirt, as it can make the bike feel light and get you out of soft ruts/corners quickly. Now for us west coasters that ride in loamy conditions in the morning and then hard pack in the afternoon, the YZ450F can be tricky to dial in. With the steel Hinson basket installed the YZ450F engine feel gets a calmer delivery to where you can accelerate sooner out of ruts/corners. The rear wheel spin that I got out of corners (under hard acceleration) with the stock basket is much less with the steel Hinson basket. Not only are you getting less rear wheel spin, but the chassis also feels slightly more planted of throttle. Installing this steel Hinson basket gives the rider slightly more front end traction off throttle on your initial lean. Yes, you will get a little more engine braking, but with the TP 5 map shown here, it does lessen the drag off throttle. 

For $310.00, it’s worth the price, if you’re looking to smooth out your YZ450F a little in the areas I mentioned. The only negative to this part is that it does make a little more engine braking, but with the map attached here, it does help lessen that somewhat. I am very sensitive to engine braking, but when I asked my other test rider to ride his YZ450F and my test bike back to back, he didn’tt notice much engine braking at all. This is a part that maybe you don't know you need, until you try it. I am glad I remembered that Hinson offers the Momentum Steel Clutch Basket. You can check the momentum basket out right here: https://hinsonracing.com/p14400-momentum-clutch-basket-2020-yz450f

If you have any questions about this test, please feel free to email me at kris@keeferinctesting.com