Twisted Development Performance Exhaust Flange

Looking for more throttle response as well as increased pulling power out of corners on your KTM 450SX-F? Although I love that smooth engine character on the KTM, I could stand to get a little more throttle response and excitement from the orange machine as well. Jamie from Twisted Development and I went through several of his performance exhaust flanges on our 2021 KTM 450 SX-F and found one size that really helped the low end response.

We weeded through three different versions of the flanges to see if any were better than stock.

The Twisted Development exhaust flanges are shaped differently than the stock OEM flange, which can change the engine character of the KTM 450 SX-F. I went through several during testing and found out a size/shape that can actually enhance the low to mid range power character. Compared to the stock piece the TD Performance flange will give you better throttle response through area 2-3 (mid to exit) of corners. Another advantage to me is that the TD flange helps pulling power out of corners as well and helps third gear lugability. The TD flange just helps the RPM’s pick up quicker, which in turn makes the KTM feel lighter when the track gets bumpy. There is no need to remap your ECU and it takes minutes to install.  

The TD flange works with the stock headpipe/muffler system or any aftermarket system. I tried it on a stock muffler system as well as a full FMF system and with both, the TD flange helped in aforementioned areas. For $200.00 bucks, to me, it’s a great way to get a little more snap out of your KTM 450 SX-F. 

Right now Twisted Development is only going to make a handful of these for the first run, so if you’re interested, you might want to call him at 951 698 7222. If you have any questions about this part you can email me at kris@keeferinctesting.com and I am happy to help.

Slater Skins Air Box Cover (Yamaha YZ250F/450F)

Remember Slater Skins? Yeah, the Blue Buffalo Supercross Team that had the complete signage/coverings across their bikes was John Slater’s brainchild, but most recently he has started to offer air box covers for late model YZ-F’s that increase airflow. We all know more air equals more power, but how does it relate to the track? I took one of Slater Skins air box lid covers out with me on a test day, to see how each performed on a 2020 YZ250F, as well as a 2021 YZ450F and found the results interesting. 

Now you might be asking yourself, why the hell do I need more power on my YZ450F? You don’t if you’re a mere mortal like me! However, if you’re looking for slightly more midrange pulling power on softer tracks as well as faster tracks with hills, this Slater Skins cover will give you a little more in those areas. Where I really liked the Slater Skins cover was on the YZ250F. The Slater Skins cover not only has front vents (with screen coverings) for increased air flow, but also more volume to allow more air inside the air box. By doing this I can really feel more bottom end pulling power out of the YZ250F as well as better low end RPM response through corners. This Slater Skins air box cover can make your YZ250F have just a little more snap out of the hole along with a slightly snappier mid RPM punch in third gear. I notice most of the mid range RPM increase while accelerating out of a corner (in third gear on the YZ250F) when the track has nasty square edge or bumps. Trying to “hop” over some of those bumps with the stock cover makes the bike feel a little less reactive to your throttle hand and heavy. With the Slater Skins cover the YZ250F felt crisper and allowed me to “pop” over bumps with a lighter more exciting feel. The difference between the stock lid and the Slater Skins lid is NOT MIND BLOWING, but it is noticeable (albeit mostly on the YZ250F). If you look at a 2021 YZ250F air box cover you will notice Yamaha put holes on the back side of the air box lid so that tells you that even the in house Yamaha R&D team was looking for increased air flow in the stock cover. The difference is that Yamaha put their vents near the back of the lid and Slater Skins incorporates the front part of the lid for increased ventilation. 

The next question is, what about the noise Keefer? Yes, it is a little louder, but to me it sounds very race bike-ish. The suction or increased noise you’re going to hear from your air box is not going to deafen you. However, I tested some other Slater Skins covers with larger vents and those were too loud and to me the power increase didn’t warrant the noise. If you’re coming off of another brand of motorcycle onto the YZ250F with the Slater Skins cover then it could be nuisance, but if you already ride a Yamaha, you should not notice a huge amount of noise. The suction noise/does get louder as you open your throttle. 

If I was needing a little more bottom end pull as well as RPM response the Slater Skins $80.00 air box lid offering is a good deal. The cover comes in white/black, but If you're looking for a blue cover, John has a blue sticker kit he can install on a black cover if need be. Blue will be available shortly. The cover comes with a washer clip for your stock dzus fastener and are available by reaching John over at slaterskins@gmail.com.   

Notes: I tested the Slater Skins cover with a stock air filter cage/screen. I have also tried it with a Twin Air Power Flow open cage/filter with even better results, but also a little louder. FYI…

Just note that your filter will/can get dirtier with the vents being up front of the lid. The screen that covers the holes doesn’t allow a ton of dirt through, but it can get much dirtier in sandier/silty conditions. FYI…

Pro Circuit Ti-6 Muffler System (2021 Kawasaki KX250)

Over 300 part number changes have been made on the 2021 Kawasaki KX250. After our first day on the new KX250 I was quite impressed with its ability to pull hard out of the corner and rev out longer than last year’s model. However, even though the Kawasaki has improved for 2021, the muffler still 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 Ti-6 Muffler System to see if it enhances the current engine character of the KX250. Here’s what I came away with… 

Immediately I weighed the both mufflers and took notice of how the Pro Circuit system cut just over 1.2 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 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 three different tracks. We tested the Ti-6 at Glen Helen, Perris and State Fair MX just so we knew exactly what we were getting out of the PC system. 

When you purchase your Ti-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 and 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 of the machine. 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 I mentioned that stock muffler has a 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 Ti-6. Doing this will give you more low end RPM response, but will hurt some mid range.

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: If you want more pulling power as well as more top end install the “Chavez Map” with your Pro Circuit Ti-6 muffler and thank me later. See below for map..

How To Save Your Subframe On Your 2019-2021 Kawasaki KX450

By: Matt Sirevaag (AKA Vaaaaaaag)

You just took ownership of a new KX450 and you want to change the engine characteristic with a new exhaust. However when listening to Keefer rant on the Pulp MX Show about A-Ray giving away mufflers like he’s Oprah on a Christmas special has you hesitant. You may wonder why the aftermarket exhaust industry didn’t just do as Kawasaki did from the factory and use a rubber grommet to help with vibration and help yield breaking sub frames. Well for whatever reason most exhaust companies mufflers are solid mounted so sometimes consumers are breaking the tabs off the subframes thus mufflers are being laid all over local tracks like toys left on the floor by a three year old.

After breaking  our muffler bracket on our KX450 test bike, we decided to take the stock rubber and mounting hardware to install the new aftermarket FMF exhaust. This is a simple mod that even the most novice mechanic can do at home. Take your aftermarket muffler and stick it in a soft vise or have your wife hold your muffler. Drill/hog out the existing mounting hole with 5/8 drill bit or step bit. Next, install the rubber grommet and hardware from your stock exhaust into your new muffler. Boom! Now you have aftermarket exhaust mounted the way Kawasaki intended it to be. You will get a small amount of float out of the rear section of the muffler, but we have not noticed any unnecessary vibration or slop when riding.

Tire Pressure Settings Bible

Riding several tires as well as compounds over the years, I decided to write some of the optimal tire pressures that I felt worked the best in a variety of conditions. Here are five major brands and their pressures, that I thought could be some benefit to you. If you're wondering what PSI to run in your new tires, look no further than the tire pressure bible below. Yes, you will see that some soft terrain tires are still categorized under the “Intermediate/hard Terrain”. That is because some soft terrain tires have an optimal feel in intermediate conditions. These tire settings are for: 80/100-21, 120/80-19, 110/90-19, 100/90-19, 120/90-19.

Pirelli:

Soft Terrain:

MX32 Mid Soft Front/Rear: 13.5/14 PSI

MX 32 Mid Hard Front/Rear: 13.5/13 PSI

Intermediate/Hard Terrain:

MX32 Mid Soft Front/Rear: 14/14 PSI

MX 32 Mid Hard Front/Rear: 13.5/13 PSI

Dunlop:

Soft Terrain:

MX 33 Front/Rear: 12.5/12.5 PSI

MX53 Front/Rear: 13/13.5 PSI

MX3S Front: 13.5 PSI

Intermediate/Hard Terrain:

MX 33 Front/Rear: 12.5/12.5 PSI

MX53 Front/Rear: 13/13.5 PSI

MX3S Front: 13.5 PSI

Bridgestone: 

Soft Terrain:

X20 Front/Rear: 13/12.5 PSI

X30 Front/Rear: 13/12.5 PSI

Intermediate/Hard Terrain:

X20 Front/Rear: 13/12.5 PSI

X30 Front/Rear: 13/12.5 PSI



Michelin:

Soft Terrain:

Starcross 5 Soft Front/Rear: 13.5/13 PSI

Starcross 5 Medium  Front/Rear: 13.5/13 PSI

Intermediate/Hard Terrain:

Starcross 5 Soft Front/Rear: 13.5-14/13.5 PSI

Starcross 5 Medium  Front/Rear: 13.5/13 PSI

Hoosier: 

Soft Terrain:

MX25S Front/Rear: 13/14 PSI

MX30 Front/Rear: 13/13.5 PSI 

Intermediate/Hard Terrain:

MX25S Front/Rear: 14/14 PSI

MX30 Front/Rear: 14/13.5 PSI 

Ride Engineering 22mm Triple Clamp and One Piece Bar Mount (Suzuki RM-Z450)

Ride Engineering’s 2020 Suzuki RM-Z450 22mm offset triple clamps (stock is 21.5mm) are anodized black, are 4.5 ounces lighter than stock and grip the fork 12mm higher up than the stock clamp. The one-piece bar mounts feature 12mm posts instead of 10mm for much-needed additional strength. The bar mounts retain the stock height and can be adjusted plus or minus 3–5mm and 5-10mm spacers are available for bar-height adjustment. Finally, soft poly cones isolate the bar post from the triple clamps, which provide additional plushness for your hands. The clamps come equipped with a steering stem and a tapered bearing pressed on, so they are ready to install once you unbox them.

The Suzuki RM-Z450 doesn’t need much help through corners, but it does need a little help in between each corner. The stock RM-Z450 is a little rigid feeling, can get a little twitchy on de-cel bumps and give the rider some oversteer when trying to load the front end on flat corners. It needs a little more stability and less of a harsh feel around the track. This is where the 22mm Ride Engineering Triple Clamps and one-piece bar mounts come into play. The clamping zones where the Ride Engineering lower clamp grip the fork leg are 12mm higher than stock. What this does is provide a different fulcrum point that allows the fork to get some additional flex. What this does is translate the RM-Z450 into a slightly more forgiving ride without sacrificing the cornering characteristics.

The 22mm offset helps settle the RM-Z450 into area 1 of corners for me as well as my test riders. With the fork set at 5mm up in the clamp the RM-Z450 now drops into a rut without that off throttle front end wiggle and the RM-Z450 now has an increase in cornering stability. Cornering stability comes into play when the rut is hammered and chopped out. The 22mm clamps provide more comfort in those conditions slightly more and allows the Suzuki to settle better. 

The adjustability of the bar mounts allows a wide range of riders the ability to dial in their cockpit area as well. For Ride Engineering weight savings and a more forgiving feel are always the goal and they seemed to accomplish this with this Suzuki set up. The Ride Engineering bar mount cones come in three durometers, which allow you to dial in the degree to which the bar mounts will give under loads. The softer the cone, the more movement you get, which increases comfort, but also can feel disconnected when you push into corners very hard. Naturally, some faster riders DO NOT like the bar mounts flexing and they prefer the stiffest of the bar mount cones, but I am more of a medium, more flex type of cone guy. 

The Ride Engineering RM-Z450 triple clamps offer some real performance value ($549.99 clamps and $104.95 for the mounts) and are offered in a cool blue and black anodized look. An investment like this should offer some sort of performance advantage on the track, not just look pretty. The Ride Engineering clamps/mounts offer a change in the handling and to me it was mostly for the better. I say “mostly” because I did feel like the Ride Engineering clamps will fade if you leave your bike in the pits, under the sun too long. Make sure to cover up your front end with a towel so that the sun is not beating directly onto the clamps anodizing.

If you’re looking for more information on this product or have nay questions please email me at kris@keeferinctesting.com. 

2020 FMF Factory RCT 4.1 Stainless Full System (Suzuki RM-Z450)

FMF has helped us on many builds and you may be wondering why do we use them so much? Well… A couple reasons are because FMF is a great American made company, they are easily accessible to us dumb media people and they actually care about the results of their product. If for whatever reason they missed the mark on a muffler setting they are willing to make changes asap to make their product even better. There are only a few companies that are easy to work within this business and FMF is one of those. 

Suzuki hasn't won a shootout or for that matter won any professional races in quite sometime, but that doesn't mean it can’t be a great bike for the motocross enthusiast. One of my photographers/test riders Dallas Dunn purchased a RM-Z450 because this is what he could afford and he wanted to ride a dirt bike. Suzuki is selling their machines at a much cheaper price than other manufacturers and that is important to the growth of our sport. We need companies like Suzuki to stick around and help this sport grow. With that being said I wanted to try and get the heavy monstrosity that is the RM-Z450 muffler system off and get an FMF 4.1 system on in order to get you guys some feedback on what it can do to the RMaRMY’s power character. 

First thing’s first. We picked stainless steel because it costs less and is more durable than a titanium slip fit joint. The titanium joints are known to wear out a little faster and you’re not going to save a crap ton of weight going to titanium. If you’re the type of rider that wants lightweight and looks then titanium is your jam, but if you’re looking to just lose some weight over stock and get some durability there is nothing “not cool” about stainless. Speaking of weight the stainless FMF 4.1 system weighs in at 6 pounds 11 ounces which is almost a three pound weight loss from the stock piece. WOW! Bolting on the FMF 4.1 system is simple and takes almost not time at all. 

On the track the FMF’s muffler pitch has a deeper more throaty pitch to it and sounds clean (with stock or lean couplers installed). We will say that you will not get a noticeable amount of more bottom end with the FMF 4.1 system installed, but what you will get is a cleaner, more linear, longer pulling power than the stock system. Out of corners you will feel more connection to the rear wheel and an overall lighter revving feel. It’s tough to find more connection when getting a lighter revving feel, but for whatever reason this is how the Suzuki’s engine and FMF system blend itself together. Pulling second and third gears longer is made easier with the FMF installed, so if you want to be slightly lazier with your shifting after the corner (leave it in second gear longer), the FMF system can provide that for you. One thing you will not be getting is more third gear recovery, so if you’re looking to lug the RM-Z450 more with the FMF 4.1, it will not magically give you a ton more pick up in third gear. That area of the power remains similar to the stock muffler character. The over-rev of the 4.1 is noticeably better with the standard coupler, but if you’re using the white (lean) coupler you may want to give the stock coupler a try again to gain even more over-rev from the stock system. For $749.99 the FMF 4.1 stainless system is a good upgrade from your heavy, slightly lethargic feeling stock muffler engine delivery. Visit fmfracing.com to get yours or you can go to keeferinctesting.com and click on the RMATVMC banner to take you to their website to purchase. 

Weights:

Stock System 9.07 oz

FMF 4.1 Stainless System 6.11 oz

Coppersmith Aero/Hybrid Fork

Coppersmith Racing Suspension has been around as long as I can remember and they have been mostly known for their Ohlins suspension set-ups. I stumbled across the Coppersmith Aero/Hybrid suspension kit for the WP AER air fork from the guys over at Racer X. If you’re on the fence about air vs. spring, the Coppersmith Aero/Hybrid fork kit gives you the best of both. It combines the old school feel of a spring fork with some of the tuneability of the WP AER fork. The Coppersmith Aero/Hybrid fork kit puts a modified Ohlins TTX22 spring cartridge in one WP fork leg for damping, with an OEM stock WP AER fork leg for adjustability. In essence, it is 50% Ohlins TTX22 (damping) and 50% WP AER (air spring). So how did it work on our Husqvarna FC450 test machine? Let me break it down for you here…

I can already forecast the emails coming in asking how it compares to a KYB conversion and a WP Cone Valve fork, so let me get this out of the way. I will give you the simple answer of the Coppersmith doesn’t have quite the comfort of a KYB conversion on braking bumps, but does have more comfort than a Cone Valve fork on small bump absorption. The Coppersmith hybrid fork gives the rider superior bottoming resistance (similar to the AER fork feel) with the cushion of a spring fork on chatter as well as small to medium sized braking bumps. For the conditions we have out here on the west coast, it really is very surprising how much different it feels compared to the stock WP AER fork. 

Compared to the stock AER fork the Coppersmith Aero/Hybrid fork will give the rider more front end feel (traction) on lean angle and give you a more consistent fork action throughout the day. I was worried that going to one Ohlins TTX damping fork leg would almost give me that half ass sort of feel on the track, but there was only a small dose of an AER feel while riding. The only time I could notice that I still had anything resembling an air fork is when I slammed into a jump face or purposely overshot a jump to flat. The Coppersmith hybrid fork gave me that AER bottoming resistance, but without that harsh end stroke spring fork bottoming out type of feel.

I was trying to find a negative feel on the track (compared to the stock AER set up) in order to elaborate more for you guys, but to me, going to the Coppersmith hybrid fork seems all positive, when moving on from the AER set up. The stock WP AER fork isn’t the worst fork known to man, that title goes to the Showa SFF Air fork, but I just can’t stomach the inconsistency that it comes with during the course of a long moto day. I want the same feel throughout the day and I just can’t seem to get that with a full air fork set up. Maybe the only real negative that I experienced is that you still have to adjust the air pressure on the WP AER side of the hybrid. But Keefer, aren’t you still working with an air spring? 

Yes, we are, but the left side AER fork will now be ran at a very low pressure (6 bar) to accommodate the Ohlins TTX 22 cartridge. Running a lower air pressure eliminates almost all of the inconsistency of a higher pressure fork setting. Yes, the air will still fluctuate during a longer moto, but to me the feeling I get on the bike during the course of the day remains much more consistent than when running higher air pressures. A lower .45 spring rate is used in the Ohlins cartridge side and running the clickers at 13 clicks of compression and 14 clicks of rebound seemed to be the best setting between a 170 and 200 pound rider.

What about the weight bias between the right/left fork legs while riding? 

Yes, I could feel a slight weight difference on initial lean on right hand corners with the hybrid system, but it was minimal and I am a very hypersensitive test rider. When letting my other test rider try the Coppersmith hybrid fork he mentioned nothing of weight bias feel (left to right) and could NOT tell a difference. 

Although we didn’t install the Ohlins TTX22 cartridge in the fork, Coppersmith offers the installation to the customer. Just ship them your right fork leg and let Coppersmith handle it for you. Coppersmith also offers DLC and titanium Carbon/nitride coating as an upgrade if you’re feeling factory. Another benefit to installing the Coppersmith Aero/hybrid kit in only one fork leg is that it saves weight over a traditional coil spring fork plus cuts down on shipping cost and retails for $995 (installed). For more information call Coppersmith at (234) 229-9059.

Yoshimura RS-9T Stainless Full System (2020 Honda CRF250R)

The 2020 Honda CRF250R is much better off the bottom end than the 2018-2019 versions, but we wanted to test the latest full stainless Yoshimura RS-9T to see if it helped the stock Honda’s engine character at all. We were specifically looking for a little more RPM response and pulling power because the Honda is still lacking some bottom to mid power when compared to the other competitors in the 250 class, more specifically the blue bike. Seeing as how my son and I have been logging a lot of hours on the machine as of late, I thought why not get a review up fairly quickly to give you the details. 

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 no swear words were thrown while installing the Yoshimura exhaust. 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) and still knocks off almost a pound over the stock system!

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 Honda pulled nicely from mid-range to the super high rev limiter that the Honda graces us with, but when exiting corners and trying to grunt up obstacles, the engine needed some help. The best way to explain the stock feeling CRF250R is that it’s just missing some meat. By saying that I don’t mean it’s slow, but I felt like I had to shift a little more with the Honda CRF250R. I had to ride 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 exhaust it was clearly a bit louder, not obnoxious, but a nice, throaty sound that was deeper and less raspy. 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 out of tight inside ruts that exited up faces of jumps. With the stock system I had to slightly slip the clutch all the way up the lip (to be able to clear the jump). When I bolted on the Yoshimura system I could leave it in the same 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 scream the bike on the exit of corners with the stock system. With the Yoshimura system I could now be a gear higher at times and use that extra meat to get me out of a loamy berm more efficiently. From mid to top end I didn’t notice any real added power gains, but I also didn’t feel like the top end suffered in order to get the added bottom end snap that I received with the Yosh. I will say that the mid rpm response is slightly crisper when in third gear as well as the recovery in third gear through deep corners. Bolting on the Yoshimura full system will not make your Honda as responsive as a Yamaha YZ250F, but it will get you a little added excitement that you could be looking for. Plus the Yoshimura mufflers look much cooler than the stock ones. 

If you have a 2020 Honda CRF250R and feel like you’d like a bit more bottom-mid range power, I’d definitely look into the RS-9T stainless system. Yoshimura offers three options, the slip on mufflers ($809.00), the full stainless system ($909.00), and the full titanium system ($1499.00). 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. 

You can check out yoshimura-rd.com for more of you can contact me at kris@keeferinctesting.com if you have any questions. 

REP Knuckle For 2015.5-Up KTM Shock

As the hours keep ticking away on the 2020.5 KTM 450 SX-F Factory Edition test machine, I have been going through test parts like crazy. I have been testing the REP (Research Engineering Performance) re-valved WP XACT Pro Components and have good things to say about Mark’s work, but I wanted to get a little more comfort for the shock, so he offered up his knuckle and pull rods to me. I explained to him that I felt the KTM was low in the rear, so I would rather not use the pull rods, but I was willing to use the knuckle in corporation with the WP XACT Pro Component shock.

So what is the purpose of the REP knuckle? The reason for designing this linkage system was to help or eliminate a common issue Mark has witnessed with the KTM/Husqvarna. A rider comment that he has repeatedly heard is a lock out sensation in the shock resulting in harshness and unwanted weight transfer. Immediately REP started testing shock settings after shock setting, which helped, but did not fix the issue entirely. This is when REP’s investigation began into the leverage ratios to decipher if this was truly a shock character issue or if the chassis needed some changes. 

The linkage put into the Austrian production has a very "stiff" ratio when compared to other brands, which is why the bikes come with such a soft rear spring. REP feels this is the right direction for the beginning to mid stroke, but the progression at the end of the stroke was slightly too aggressive causing unwanted weight transfer and harshness from the rear of the bike

The REP linkage system makes a more linear progression for models 2015.5 to current. Many of the other companies producing linkages for these bikes result in a softer ratio all the way through the stroke, which is why they also require a stiffer rear spring. The REP system does not stray far from the production ratio for the majority of the shock stroke, but simply tapers off from mid to end. This change does not require a spring change because the ratio from full extension to rider sag point is very similar, but once active on the track the rider will see the digression in the ratio to be quite apparent.

The knuckle can be used with the standard pull rod (like what I did) or the longer REP version. If only the knuckle is used the rear seat height will be raised 1.9mm, but if the entire REP linkage package is used the rear will be lowered 2.1mm when compared to stock. Keep in mind if the entire package is used, it not only lowers the rear, but also exaggerates the flatter ratio that the knuckle is producing. REP recommends the knuckle to all his riders, but Mark decides if the customer needs the pull rod based on the rider's preference and comments.

A couple positives to the knuckle that I noticed right away was comfort on acceleration through deep/choppy ruts and the KTM felt less active on de-cel bumps coming down hills. Without the REP knuckle the KTM kicked me in the butt more than other Japanese bikes do when braking hard on de-cel bumps, but with the REP knuckle the rear of the KTM stayed planted better and gave me a calmer feeling when pushing deeper into rough corners. I managed to get a bone stock 2020 KTM 450 SX-F, (without XACT Pro Components) installed the REP knuckle on the WP shock and it gave me the same feelings in those two areas of the track. I appreciate that I didn’t have to drop a spring rate and basically could just bolt this on and feel an improvement. For $249.95 for the knuckle (with bearings installed), I really like the way the KTM can be pushed harder later in the day when the track gets hammered. I used to shy away from the KTM in the afternoon hours, because it would beat me up a little. Now by adding this REP knuckle to our KTM Factory Edition, it has made this a more comfortable machine to ride when everyone else is packing up to go home. 

Note… Not all aftermarket knuckle/linkage systems work on every brand of motorcycle. Some manufacturer R&D teams get their linkage ratios correct for the masses upon production, but it’s refreshing to see Mark at REP sell a suspension piece for the KTM that actually is noticeably better when riding it back to back with the stock piece. 

FAQ: 

Kris, how do I know if I need a knuckle and not just a re-valve on my shock?  

If you are experiencing a firm feeling coming out of corners and seem to lose traction, this knuckle can help. If you are coming into braking bumps and notice that the KTM has a nice plush feel on the first bump, but then gives you a rear end kick when unloading upon the second touch, this knuckle can help that. These are the two areas that most weekend warrior riders would feel the REP knuckle is better. 

Kris, how do I know if I want the REP pull rods to go along with the knuckle? 

If you want your KTM to feel a little lower in the rear and want more rear steering, then you should look into the REP pull rods as well. I am a big front end steering rider so having the rear end a little higher for me fits my riding style. 

Attached is a graph from REP. The red line is the REP vs the black line Production.

Kreft Suspension Review (Husqvarna TE300i)

Written By: Michael Allen

Let’s be honest, as riders we have all probably uttered these words to a suspension tuner, “I want it plush, but stiff”. I would imagine that every suspension guy has heard that phrase and grits his teeth every time he hears it. That is where Kreft comes in with their revolutionary design of being able to “revalve” the fork with just the turn of a dial instead of taking the fork apart and actually putting different shims in the fork itself. Admittedly when it comes to the internals of how a fork works I am no specialist, but when Matt from Kreft broke it down and explained it to me in dumb dirt bike rider terms, it was very interesting and made a lot of sense. 

I have worked with many suspension companies over the years and for the most part they work the same in terms of pick up and drop off. This is the first thing that stood out to me when I started working with Kreft: The first step of the process is an initial phone consultation where you actually build somewhat of a relationship with the representative. You go over the basics, like what bike you’re riding and your measurements, but you also get into what you want to feel out on the trail. Along with that you get a crash course on what makes Kreft different and how their system works. From there they send you an empty box with prefect (I really mean perfect) cutouts for your specific fork and shock. They are so detail oriented they even send you bleeder screws, so just in case you have button bleeders they can be replaced so that your forks don’t leak and ruin the box in transit. The professionalism is second to none while still being personable as well as very helpful and explanatory.

Aside from the obvious spring rate change and re-valve, the fork gets Kreft’s “Re-valve Control”. The way it was explained to me was that on a standard fork the shim stack nut is tightened down on the top of the shims and in that case, the valving is whatever the tuner’s spec is. The valving itself cannot be changed without fully dissembling the fork and changing the actual shims. The only adjustability on a standard fork is compression and rebound clickers. What Kreft does is use a spring that can have more or less pressure put on it with the adjustment of the re-valve Control knob on top of the left fork. What that spring pressure does is put more or less pressure on the shim stack itself. This gives the rider the ability to make “valving changes” on the fly to adapt to a wide range of terrain and disciplines of off-road riding. With the Kreft fork you now have the standard compression and rebound clickers as well as the re-valve control. In doing all these changes Kreft has also changed the damping forces in the left and right fork tubes. The XPlor fork has unbalanced forces in stock form, making the left tube do the majority of the work. What this does is give the left fork more of a chance of having oil cavitation, resulting in poor damping performance. The final thing that was done to the forks was the Microfinish which is said to work better than DLC coating (and is far cheaper) to reduce friction creating less drag and seal stiction than the stock finish.

To compliment the fork changes, Kreft internally changes the shock components to get the greatest potential and best balance of the low and high speed tuning circuits. If the circuits aren’t balanced and one is doing far more than the other there is a greater chance for cavitation which results in poor performance. Once the circuits are balanced and cavitation is no longer occurring, the changes that are made to the clickers have a much larger adjustment range and are far more effective. Along with the spring change on the shock, Kreft also installed the X-Trig preload adjuster which I had never used, but holy shit that thing is awesome!

Now that I have explained all the technical info (to the best of my dumb dirt bike test rider ability) let’s get down to how it all works out in the real world. As I said in my initial test of the TE 300i, any type of riding other than very tech slow trails meant that the TE was going to feel out of place. The fork was extremely divvy when on the brakes or even just when transitioning off throttle. This unbalanced pitching feeling caused the bike to be unpredictable when cornering. In addition to that, anything that resembled a g-out made the bike bottom and rebound too quickly, which doesn’t necessarily give the rider very much confidence, especially in a racing situation. The one race that I did in stock form made it clear that I was having to check up for obstacles that normally wouldn’t phase me, so I knew something had to be done. 

After getting the stuff back from Kreft I bolted it on and read through their extensive welcome packet, which was super informative. I set my sag (which they had very close already) and headed out to my favorite trails, which have a plethora of different types of terrain. The first thing I noticed was that the unbalanced feel was no longer an issue. Now when I enter coroners the bike stays further up in the stroke and is much more predictable. My biggest concern was that after telling Kreft that I mostly ride faster paced desert terrain, I was worried that they would make it too stiff and I would no longer have the compliance in the tight technical terrain. Like I said in the beginning of this story, I basically told them that I want it firm, but soft and to my surprise, Kreft gave me my cake and let me eat it too. After becoming more confident and being able to pick up the pace, I found myself going into g-outs as well as slamming into bigger whoops with more speed. Initially the fork had a slight quick feel that would cause the front tire to lose traction, but after slowing down the rebound three clicks, the bike stayed planted much better following hard landings.

The only other issue I had with the front end was that I felt I still needed more bottoming resistance. I tried going in on the re-valve control, but that wasn’t necessarily the feeling I was looking for. While going in on the re-valve control helped my issue, it took away a little of the initial plushness that I liked. After talking with Kreft, they recommended I simply get a syringe and add 15ml of oil to both forks. After doing this I was able to keep the initial settings on the re-valve control while still getting the bottom resistance I was looking for. When it came to the shock, Kreft was really close on the setting I loved out of the box. I had a slight kick in the rear on de-cel bumps, but it was only off-throttle. To combat this Kreft recommended that I open up the high speed compression all the out. After doing this the kick was eliminated, but I felt the bike was bottoming too frequently, so I followed their recommendation and worked the high speed adjuster in by ¼ turn at a time until I found the balance that I desired. One misconception that I think a lot riders have (I used to as well) is that if your bike is bottoming it’s too soft. It’s perfectly ok for your bike to bottom if the bump or landing warrants it. Bottoming out from time to time means you are using all of your suspension travel. This is what you want! Use all the travel, but still have a comfort/performance blend for your type of riding.

Kreft prides themselves on having great customer service, provide a high end product and also a product that has a very wide range of adjustability. When they told me that I could ride technical single track with the same bike that I rode at the moto track, I was skeptical. My last test before writing this article was doing just that, I went to the moto track. Before riding I looked at their recommended setting for moto, adjusted it and started moto’ing. Now was it just as good as a moto setting would be if the suspension was built for moto? Not entirely, but the adjustments for moto made the bike comfortable enough on the track that I was jumping every obstacle without blowing through the travel as well as cornering with confidence. I didn’t feel like the suspension was holding me back by any means and I wasn’t out of my element on this bike. The mere fact that one bike can be capable of such different disciplines with small adjustments is super impressive. I think that Kreft is really on to something and will only be getting more recognition as time goes on.

The price breakdown is as follows: Xplor Re-valve Control and Re-valved shock is $1,200 (including seals and fluid), the addition of springs (if needed), Microfinish and X-Trig spring adjuster brings the total to $1,800. Like I said before, Kreft prides themselves on being very high end and in my opinion you get what you pay for. Every part of dealing with Kreft was top notch, from their box, customer service, quality of parts, and performance of the suspension was very impressive. If you are in the market to fix your 4CS, AER, or Xplor suspension, I would highly recommend giving Kreft a call. If you have any questions about the performance of the Kreft setup on the TE 300i feel free to reach out to me at Michael@keeferinctesting.com. That being said, if you have any technical questions about the parts itself reach out to them because I’m just a test dummy and won’t be able to answer your questions. Kreft’s contact is 541-797-0700 or email them at Info@Kreftmoto.com. 

Recommended Handlebar Specs For 2020 MX Machines

When it comes to handlebars I am a pain in the ass. The height, width, rise, and position is very important to me between each bike that I test. I find that you can’t run the same handlebar bend on every bike, even though I like a bend on one bike, sometimes it doesn’t feel as good on another. Every bike has a different rider triangle so you must adapt to different bar bends if you change motorcycle brands. As the years progress, dirt bikes evolve as well as their dimensions so don’t be that rider who sticks with a Honda High bend that you ran back in 1997. As you may have heard in my “Handlebar 101” podcast (show #70), if the bar feels too low (height), you should try to get the bar height from your bar mounts and not the handlebar itself. Getting the height from your bar mounts allows you to keep proper technique (position) through corners (where most of the time is made up on a track). This article was a big hit last year and by the shear number of emails I get about handlebars, I wanted to update some bends for 2020. Here are some of my favorite bar bends right here for 2020 as well as a recommendation on bar/bar mount heights for different sized riders.  

As you will notice most of these handlebars on this list are Pro Taper and Renthal. This doesn’t mean that I am trying to sell you on these handlebar brands. This is just what I personally like myself and should be taken as such. If you like another bar brand, that is fine, simply look at the dimension of the preferred handlebar and try to mimic that dimension to your favorite handlebar company. There are tons of handlebar companies out there, but for me, Renthal and Pro Taper are the bars that I prefer. Again as always for testing purposes, I tried a wide range of handlebars in my shootout so go give that podcast a listen when you can (Show #70). There are some great options out there. Again….This doesn’t mean other handlebars are crap. For transparency reasons, I am letting you know that these are the companies I prefer. I receive ZERO dollars from Renthal or Pro Taper.

• We are using 2020 models for reference, but if you have an older model and are concerned on which handlebar to run please feel free to email me at kris@keeferinctesting.com. 

• All Dimensions are in (MM). 

2020 HONDA CRF 450R/250R:

Notes: The stock bar bend on the 2019/2020 Honda CRF 450R/250R has finally been updated to a bend that is lower and flatter than previous years. This bend is actually quite good and we usually leave the stock Renthal handlebar on the Honda. If you think you would like more flex you can try the optional bar bend below.  

Preferred: Stock Renthal 839 FatBar (W)802 (H)91 (R)52 (S)51 

Optional For More Flex: Pro Taper EVO SX Race (W)800 (H)87 (R)54.5 (S)54

Optional For 6’0-6’2: Factory Suzuki (W) 800 (H)92 (R)62 (S)47

Bar Mount Height: Stock 

2020 YAMAHA YZ450F/250F:

Notes: Yamaha also did a good job on creating a bar that is fairly neutral for different sized riders, it’s just too bad their seat and footage height is all screwed up for taller riders. It’s lower height seems to fit a wide variety of riders (5’8-6’0), but taller riders may want to put the bar mounts in forward hole/back position.  

Preferred: Pro Taper EVO SX Race (W)800 (H)87 (R)54.5 (S)54

Optional 6’0-6’2: Renthal Fatbar 602 bend (W)801 (H)89 (R)59 (S)56

Bar Mount Height: Stock 

2020 KAWASAKI KX450/250: 

Notes: 7/8 lives on! Kawasaki managed to keep the good ol’ 971 Renthal 7/8 bars, which are pretty damn good! I like a 7/8 bar and I actually stick with the 7/8 theme if I can. The 7/8 bar does bend a little easier, but you get a lot of flex when the track gets rough. If you’re an aggressive rider who likes a little more positive steering than go to a 1-1/8 handlebar for increased stiffness. 

Preferred: Renthal 7/8 983 bend (Villopoto/Stewart) (W)808 (H)95 (R)58 (S)55

Oversize Crossbar Option: Pro Taper Fuzion Henry/Reed (W)800 (H)92 (R)66 (R)40 (S)55

Optional For 6’0-6’2: Pro Taper EVO Factory Suzuki (W) 800 (H)92 (R)62 (S)47

Bar Mount Height: Stock

2020 SUZUKI RM-Z450/250:

Notes: The stock Suzuki bend has some sweep to it, which makes the bike feel small at times. I prefer to open the cockpit up a little. 

Preferred: Pro Taper EVO SX Race bend (W)800 (H)87 (R)54.5 (S)54

Optional: ODI Podium Flight CountryBoy bend (W)803 (H)92 (R)56 (S)52

Optional For 6’0-6’2: Pro Taper EVO Factory Suzuki (W) 800 (H)92 (R)62 (S)47

Bar Mount Height: Stock

2020 HUSQVARNA FC450/250:

Notes: Husqvarna comes with a very low bend and that fits the ergos of this bike, but the width of the bar is too long. I actually like the stock handlebar bend on the Husqvarna, however I cut the handlebar down to 803mm, which really helps the character of the Husqvarna when leaning into corners. 

Preferred: Stock Pro Taper EVO handlebar cut to 803mm (W)811 (H)80 (R)39.5 (S)51

Optional: Pro Taper EVO Carmichael bend (W)800 (H)77 (R)40 (S)55

Optional For 6’0-6’2: Pro Taper EVO Factory Suzuki (W) 800 (H)92 (R)62 (S)47

Bar Mount Height: Plus 5mm 

2020 KTM 450SX-F/250SX-F:

Notes: The stock bar bend shape on the orange brigade is also decent, but it’s too stiff and long. If you don’t think it is too stiff, you can simply cut the bar to 803mm and run it! 

Preferred: Renthal 821 bend cut to 803mm (W)813 (H)78 (R)42 (S)54

Optional: Pro Taper EVO Husqvarna Stock cut to 803mm (W) 811 (H)77 (R)40 (S)55

Optional For 6’0-6’2: Pro Taper EVO Factory Suzuki (W) 800 (H)92 (R)62 (S)47

Bar Mount Height: Plus 5mm

Fastway Air EXT Foot Pegs

Fastway Air EXT pegs are on a mission to reduce ankle injuries, or at least limit the severity when an impact goes wrong. The basic idea is a wide but fairly conventional 2024 billet aluminum footpeg with a teardrop-shaped sort of heel peg welded to the rear of the normal peg. The teardrop ankle-saving portion isn’t welded at the same level as the footpeg however. The contact point is lower than the surface of the peg, but the patented height, traction, and camber (tilt) adjustability, is fully customizable. The idea being that you never feel the Air EXT pegs until you suffer an extreme landing that puts excessive loads on your feet and/or ankles. The Universal Collar System (UCS) lets you customize your mount in either the stock or lowered positions on most bikes – simply by reversing the collar. Fastway’s patented replaceable traction cleat system allows you to customize the shape and traction level of your foot bed as well.

The reality is that you do feel the Air EXT’s rear portion fairly often on the track, but I only felt it in positive ways. No question, when you land short or long, your feet, ankles and even knees would be smiling if they had lips. Impacts that clank the suspension hard enough to hurt your ears don’t bother my 42 year old ankles. The Air EXT’s look like they will would limit the kickstarter, if you still have one of those, but they didn’t on our Suzuki RM-Z250 when we tried them on that machine. Perhaps if you were sloppy with foot placement, your boot heel could contact them and that would be annoying, but we didn’t have a problem. In whoop sections and while approaching jumps while standing up, you can even incorporate your heels to load the suspension to get increase height, similar to a seat-bounce. The bigger your feet, the more likely you are to feel the rear portion of the peg and that means in a positive way-absorbing abuse-and just being aware that it’s there. I wear a size 11, and I’d probably like the teardrop portion better with the teeth slightly dulled a little, but then again after about a couple hours on the pegs I was getting more used to them. I have never really feared landings, but I can appreciate what these pegs offer riders with Achilles and ankle injuries. Or maybe you’re learning how to ride on the balls of your feet, the Air EXT’s give the rider confidence when placing their feet back, when getting to the correct attack position. Ask Ryno how important riding on the balls of your feet are! #TwoChickens

While riding through deep ruts, these pegs can help allow large footed riders place their feet on the balls to keep their toes safe. I have had a couple of our bigger testers try the Air EXT’s and they comment they have less ankle/knee fatigue at the end of a long day of moto’ing. The Air EXT’s are like virtual floorboards for your dirt bike. The thing you have to remember when riding with these pegs is that the space to the rear brake pedal or shifter is greater. You will have to cover more ground and remember that when trying to make a shift or use the rear brake, when riding on the back of the Air EXT’s. 

I ended up going with the smallest cleat option on the pegs as those provided enough traction without feeling too tall on the bike. If you’re on the shorter side you could definitely benefit from the replaceable cleat height design and the difference it can make with your rider triangle. I didn’t however try the Universal Collar System (UCS) yet, which allows you to lower the footpegs from the stock position, but plan to with a couple test machines soon. 

At $255.95 for the Air EXT pegs and $19.99 for the fit kit, it’s not a cheap aftermarket footpeg purchase, but this is still a less expensive option than some other titanium offerings out on the market. Check these pegs out at Fastway.zone.com.

Specs:

•Weight: .85 pounds per set

•2024 billet aluminum

•Unique universal footpeg

•Precision engineered, manufactured, and assembled in the U.S.A.

•All footpegs ship with 2 sets of F3 threaded cleats– short 10mm, and tall 12mm cleats

•Requires Fastway Footpeg Fit Kit 

ETS US MX 18 K2 Racing Fuel

Not everyone has the money to go purchase race fuel for their dirt bike. High end race fuel is something that maybe only a few serious racers really want. I can relate and understand this. That shouldn’t deter other media testing outlets away from testing such fuels, but it seems like you can’t find that much real world testing info about such things. This test may not be for everyone, but I feel like I wanted to really see how much of an improvement (on the track) race fuel can make in a machine when properly mapped for modern four-strokes. With most high end fuel, simply dumping it into your bike and riding is not going to benefit you in any way, so stop wasting your money if your bike/ECU isn't tuned for it. There are some other direct pump replacement fuels that DO NOT need re-mapping, but for this test I wanted to try and get the most out of what I am pouring in. I mean it’s $26.00 a gallon, so we have to be “ALL IN” when going this route right? More on that price later… ETS Racing fuels are based out of France and have been around for 12 years, but maybe you’re not too familiar with the company, so here is a breakdown of the ETS US MX 18 K2 racing fuel.

About The Machine I Tested The Fuel With: I chose the 2020 KTM 450 SX-F Factory Edition to test the ETS Racing Fuel because it’s one of the 450’s that I feel that can benefit from quality race fuel the most. The KTM 450 SX-F has a smoother power delivery with a stock ECU setting that is slightly rich/lethargic feeling. I also have been doing some “other” modifications along they way with this model and have seen very solid improvements. Each modification that I have done to the orange brigade has made this machine better with each chunk of money that I have thrown at it. That is what you expect when you put money into your bike right? Well, that is not always the case because sometimes putting your money into your bike doesn’t mean it gets better. Putting the money into the right modifications is key and that is what we have done to this 2020 KTM 450 SX-F Factory Edition. Our 450SX-F has a XPR Performance Vortex ignition that is mapped for ETS US MX K2, VP MR Pro 6, and regular super unleaded pump fuel. The beauty of the Vortex ignition is that you have 10 preset maps that you can go back and forth from so it makes it simple to adjust when your pocketbook does. The simple fact that the ignition is super consistent and hasn’t given me any problems is just one reason why I went this route. The engine is completely stock (minus the FMF 4.1 Muffler System) and I wanted to keep it this way for durability reasons. I ride the crap out of the Factory Edition and I DO NOT need to be rebuilding it every 20 hours.  

What Sparked My Interest To Test The ETS Racing Fuel: Number 1….Not a lot of people know about ETS Racing Fuel and who’s using it. Factory Red Bull KTM and Rockstar Husqvarna race teams use and endorse the fuel. In fact, ETS doesn’t “give” those teams fuel, because in reality both teams “purchase” the fuel. This sparked my interest because it’s not everyday that teams are “spending” money on pieces to their factory bike puzzle. Most of the time factory teams test parts and said companies provide them with that product for free (or even pay them to run their product)! Number 2…We have a ton of ethanol based super unleaded pump fuels around California and this has caused a couple fuel pump failures for me in the past on other machines. Number 3…Once Chad at XPR Performance put on the Vortex ignition he told me there was a map preset for VP MR Pro 6 and ETS US MX 18 K2 racing fuel, so I went ahead and got some of each. Number 4…I tested with the VP MR Pro 6 for a while and noticed a nice gain in pulling power (compared to pump fuel), but it boiled on warmer days in California. I really liked the power gains I felt, but after 16-18 minutes of hard riding the KTM began to run noticeably slower, had a dirty low end feel and ran inconsistent. This really sparked my interest to see if another competing race fuel could give me the same power gains, but more consistency over the course of longer motos. 

So How Did the ETS US MX 18 K2 Stack Up Against VP’s MR Pro 6 On The Track?: First thing’s first. This seems unimportant, but If you’re a die hard moto guy you will really love the smell of the ETS US MX 18 K2 racing fuel. It’s a sweet smell and if you have walked around the pits of an AMA Supercross, I am sure you have picked up the scent. However, other people may not appreciate the smell (like the wife), so you may want to store the fuel somewhere far away from the living room or kitchen area of your home (just in case your garage is close to these parts). Once the KTM fuel tank was emptied and the ETS was poured in, I headed out on the track to do a longer minute moto. I made sure to test all three fuels (VP, ETS, Pump) on the same day (over the course of a few days) in 90 degree temps for an apples to apples comparison. The first thing that I noticed with the ETS US MX 18 K2 racing fuel is that the KTM 450 SX-F had better throttle response (than that of the VP). Throttle response was slightly more crisp and instant with a better bottom end pulling power out of corners. You can just feel a little more “meat” when rolling on the throttle. Mid range was also improved slightly, especially when I was rolling sweeping corners in third gear. The KTM just seemed to pull better and have increased mid range RPM response. The VP and ETS fuels feel very similar up on top end as I didn’t notice any real difference there. To me the biggest selling point (besides increased power feeling) was the consistency the fuel had over the course of a 30 minute moto. With the VP MR Pro 6 I had a clean running engine feel up until 18 minutes and then it started to boil (on very warm days), but with the ETS fuel the KTM ran crisp and clean throughout the entire moto. This was huge for me! There were no remnants of fuel puking out the vent house and I could do a full day of motos with zero boiling issues. 

So How Did the ETS US MX 18 K2 Stack Up Against VP’s MR Pro 6 HT On The Track? Yes, VP makes a “high temp” MR Pro 6, but I noticed that I lose a little more pulling power with the HT versus the standard Pro 6. With the ETS MX 18 K2, the KTM not only doesn't boil, it simply outperforms the VP Racing Fuel “HT” in torque feel as well as excitement (throttle response).  

Cost And Where To Purchase: You may want to sit down for this. Ok, you ready? Are you sure? The cost of the ETS US MX 18 K2 racing fuel is $26.00 a gallon and comes in 15 gallon drums. Again, like I mentioned before, this is an expensive investment that is not for everyone, but if you’re serious about performance and getting that little extra, this is a great alternative race fuel that is CONSISTENT! The VP MR Pro 6 fuel is slightly more expensive compared to the ETS US MX 18 K2 fuel so if you’re already purchasing high end fuel, this will not be a big shock to you. You DO NOT need an aftermarket ECU to run this fuel, but you will need to get your stock ECU re-mapped (if available to you) to reap all the benefits of this fuel. The ETS fuel usually makes your machine run a little richer than that of the VP MR Pro 6, so leaning out your bike a little is a good way to go. There are plenty of engine builders who are familiar with mapping ECU’s to this fuel so please feel free to email me and I can give you some recommendations. If you are looking to get a drum of this fuel you can go to etsracingfuels.com and order through their website directly. They offer free shipping on orders over 40 gallons so it’s nice to have fuel delivered to your door. Any questions about this test please feel free to email them to kris@keeferinctesting.com 

TYPE | UNLEADED GASOLINE
RON | 102MON | 86OXYGEN | 3.9 %OCTANE | 94DENSITY | 762 KG/M3
REGULATION | AMA

Vortex Ignition For 2020 YZ450F

The Yamaha YZ450F comes with the Yamaha Power Tuner App that allows you to change the parameters of the bLU cRU’s ECU settings. It allows the consumer to customize their YZ450F power delivery, so that they can enjoy a more friendly power character or a more aggressive type of delivery. While this system works very well for the average consumer what about the rest of us that may want to tune their YZ450F even further? What about having an ECU that has wider parameters and an ECU that can give you more horsepower, but make it rideable as well? Can we make our YZ450F even better with an aftermarket ECU? Is there a big enough difference in power delivery that it warrants spending an extra grand on an electrical part? I wanted to find these questions out, so I called upon Chad at XPR Motorsports to see if he could map a Vortex ignition for my 2020 YZ450F in order to see if it wold actually make it that much better. 

Unlike a KTM 450 SX-F it is very difficult to improve upon the Yamaha’s engine character. The YZ450F is the best production motocross machine made at this moment, so the gains are tougher to get through the aftermarket unlike the orange model. With a KTM I can slap on a Vortex ECU and immediately notice a huge difference in power as well as traction. However, I have been playing with the Vortex ECU on the Yamaha YZ450F for almost a year now and found out that it’s not that easy to make the Yamaha’s engine “better”. Chad at XPR Motorsports is one of only two people in Southern California that I would trust to help me with ECU testing (the other being Jamie at Twisted Development). I told Chad that I don’t necessarily want “more power” from the YZ450F, but I wanted more rear wheel traction with a broader, longer power (similar to a KTM 450 SX-F power spread). I can roll my corners really well on a KTM because it is so damn smooth off the bottom and I wanted to see if we could get some of that character on ol blue here.  

I am not going to sit here and tell you that getting a map that actually made me happy was easy because I think I gave Chad a headache more than once while doing this test. However once we honed in on what I was looking for, it was something that the stock Yamaha Power Tuner simply couldn’t do. With the help of XPR’s mapping and the desired power that I was looking for, I now had an easier to corner Yamaha YZ450F, with more traction out of area 3 (end of corner), as well as a broader/longer overall top end/over-rev. 

I wanted to keep the third gear lugability, but also make second gear more usable so I could make shifts later once exiting corners. This wasn't easy to achieve as Chad and I quickly found out. I got a longer second gear, but was losing some of that easy to ride third gear lugability because the engine was much freer feeling with the Vortex ECU. With a lighter engine feel you get less de-cel pitching, which is great because the chassis stays calmer, feels more exciting, has better recovery, but you also get less chugability when lugging your engine. Chad went went back to the drawing board and gave me another map that split the difference for me and made me really happy. I now had most of that third gear roll on lugging power, but still retained that free feeling engine feel that I loved when the track got rough. Having less engine braking on the YZ450F really helps this chassis stay calm when diving deep into corners with large bumps. 

I like that the Yamaha YZ450F is easier to start as well as fires up sooner with the Vortex on, so having this ECU on could really benefit a dead engine type of off road rider. With the XPR mapped Vortex, the mapping seems crisper/cleaner and never had a de-cel pop that I sometimes experienced with the TP 3.0 map. We mapped the Yamaha to a Pro Circuit exhaust and originally started with VP Pro 6 fuel, but that was simply too much power down low for me, so creating a map for VP T4/pump fuel made the Yamaha engine much more manageable in hard pack situations. 

The bad news about going to the Vortex ECU is that you lose all of your Power Tuner functions like the maintenance schedule, running time, etc. The Vortex comes with 10 pre-programmed maps as well as three fuel trim knobs that can help with your “Lo”, “Mid” and “High” rpm ranges. This is not an inexpensive mod, but it can help broaden the Yamaha’s power, make the hit more seamless down low as well as help the chassis when pushing the machine when the track gets rough. 

Is the stock ECU good? Yes! If you feel like the stock ECU/Power Tuner App has enough parameters and you’re happy, you DO NOT need an aftermarket ECU like this. 

Do I feel as though the Vortex ECU makes as big of a difference on the Yamaha like it does on the KTM 450 SX-F?  No, I don’t. The Vortex ECU on the Yamaha helps make it easier to ride, but Yamaha R&D did such a great job with their mapping that it may be hard for less picky riders really notice. KTM’s stock ECU mapping is not nearly as good off the show room floor, so the difference from going to a stock ECU to a Vortex on a KTM is noticeable by a wider range of riders.  

Who is this Vortex ECU for? This specific ECU on the Yamaha is for riders who love the stock engine character, but want a little more control off the bottom and more pulling power from second and third gears. Oh and how could I forget that this is not a cheap mod (at around a $1000.00), so you might have some coin saved up in your bank. 

Would I purchase this mod myself? Yes, but I am the type of guy who still likes to be competitive at the ripe old age of 42, likes to have a linear, longer power delivery and loves to tinker with stuff. If you’re like me this mod will make you smile. 

Conclusion: Overall I am happier with the Vortex ECU on the 2020 YZ450F because the bike has more controlled power and it makes it less work for me to ride harder. The downside is coming up with the 1K to purchase it! Guess I will be impatiently waiting on my stimulus.

Contact: Chad @ XPR Performance (951) 813 8873

Ride Engineering Full Performance Linkage (Husqvarna FC450)

Getting that comfortable feel as well as increased track toughness can be somewhat hard to find on the Husqvarna FC450. At least for me anyway. I can go to tracks that are soft and tighter and be completely happy with the Husqvarna and then go to a fast/choppy track that has more flowing corners and be confused on why this bike feels so different. I know a couple companies have been making different linkage ratios for the Husqvarna and KTM’s, but I wanted to try Ride Engineering’s performance linkage system on the FC450 to see if it actually improves upon the ride comfort on choppy tracks. 

 You might be saying to yourself, well what about the KTM Keefer? I do similar negative feelings on the KTM that I do on the white bike, but the Husqvarna does seem like it’s slightly more forgiving at times on rougher tracks. As you may already know this link also can work on the KTM, so if you’re on an orange bike, this test could also apply to you. I will be doing a full review on a couple different linkage systems (Ride Engineering/REP) on the KTM in the coming weeks, just to see if I can feel a difference between each. 

So what exactly am I looking for here? Why is there a need for a different linkage ratio on this machine? Why didn't the R&D team at KTM/Husqvarna choose the ratio that Ride Engineering came up with in the first place? I will give you some insider knowledge on the R&D process a little before we dive into this test. Sometimes when OEM R&D teams test suspension, often there is a few linkages that the test riders have to weed through to see which one works best for a wide range of riders on said bike. Setting up a bike for the masses is not easy to do and most of the time the OEM’s choose a setting that is more of a “comfort setting” than a performance setting to offset the stiffness of the chassis. Comfort is needed on any new production motocross bike and getting a suspension spec that coincides with the correct linkage ratio as well as frame stiffness can be tricky. Not every bike benefits from an aftermarket linkage ratio, so don’t think you need a linkage on every bike on the dealer floor. If you’re happy with the feeling that you get when you ride your machine then try not to overthink it. JUST GO RIDE! If you feel what we are describing in this test then possibly a linkage could benefit you. If you DO NOT feel the things we are explaining in this test, you can simply disregard it and move on to something else you want to add to your FC450.   

What I Want Out Of The Rear Of The Husqvarna 2020 FC450?

The rear of the Husqvarna FC450 feels somewhat rigid on acceleration chop and I can feel like my rear end is dancing around when hard on the throttle out of rough corners. I spent some days searching for some added traction/comfort by changing sag settings, spring rates and clickers, but came up empty handed. I also tried a WP Pro Component shock and that just exacerbated my problem a little more on acceleration, creating a firmer feel out of corners. Even though I had more hold up and less fade with the Pro Component shock, I wasn't happy with my acceleration feel. 

What Did I Get Out Of The Ride Engineering Performance Linkage? 

Ride Engineering recommends that you go up a spring rate with their linkage, but I wanted to try it with the stock 45 N/m spring rate as well as a 48 N/m. The Ride Engineering pull rods are 1.3mm longer than the stock rods and the knuckle is more progressive, so it ramps up different than the stock knuckle. Once installed and the sag was set to 104mm, I immediately felt slightly more comfort out of the rear of the bike on acceleration, but also noticed it being a little low for my liking in that area. On steeper jump faces or flat landings I felt like the shock bottomed and felt empty on high speed compression. After increasing the high speed compression, it helped a little on jump faces as well as helped the empty feel on slap down landings, but it hurt acceleration traction. I installed the heavier 48 N/m spring on, reset my sag, jumped back out on the track and was quickly greeted with a firmer feel, but the firm feel didn't translate into a harsher rear end like the stock linkage/spring had. 

The rear of the Husqvarna stayed up in the stroke more out of corners, but also had a freer feeling to it, which increased my rear end traction. Another positive to the heavier rear spring/Ride Engineering linkage combo was that the control of the Husqvarna was better when hitting de-cel bumps at speed. At times with the stock shock/link, the Husqvarna would ride too low and have a sudden kick to the rear end that left me with a sensation of less control leading into corners. With the heavier rear spring and Ride link the initial braking bump feel was firmer, yet the FC450 moved less when getting to the fifth, sixth, and seventh braking bump into corners. I could hold on the throttle a little longer because I had more control as well as better action of the rear end. If there was a negative to the heavier spring/Ride Engineering link, I would have to say that it can make the Husqvarna a slightly slower cornering bike on initial lean, but to me I didn't mind the slight slower turn in feel. I know some of you may not like that, but if you find that this is bothering you then simply run your sag at 103mm and this can help initial turn in. 

Like I mentioned above, I tried the WP Pro Component shock with the Ride Link set up and it gave me a similar feeling that the stock shock/Ride link set up did, but with even more hold up when ridden aggressively (of course that has something to do with the valving as well). I liked that with the Ride Engineering knuckle/rod set up of the FC450 felt less firm on acceleration and yet still had more control on de-cel bumps. 

This Ride Engineering Performance Link is $449.90 and is available over at ride-engineering.com and fits current Husqvarna/KTM models. 

If you’re a KTM owner and looking for a little comparison, stay tuned for a REP/Ride Engineering Performance Link comparison as both companies make a different knuckle ratio for the white and orange machines. Will I be able to feel the difference? Find out soon! 

2020 Honda CRF450R Three Way Muffler System Comparison

The 2020 Honda CRF450R is a popular machine. After all of my years with Dirt Rider Magazine as well as doing my own thing over here at Keefer Inc. Testing there has been one thing that hasn't changed… The amount of page views and questions that I get about the Honda are always more than any other color! As a test rider, I like the Honda CRF450R because it’s one of the most difficult bikes to set up for a wide variety of tracks, so that keeps me trying different products and thinking of ways to try and make it better. As a consumer or a local racer, the 2020 Honda CRF450R can drive you nuts at times right? It’s super fun to ride, but sometimes can be a handful at certain types of tracks.

In this article I am going to test the Yoshimura RS-9T, FMF 4.1 RCT, Akrapovic Evolution titanium muffler systems for the 2020 Honda CRF450R and give you some feedback on each one’s engine delivery character. I picked these three muffler systems because they have been one of the best three that I have tried on this particular machine. This isn't a shootout as much as what each system can bring to the table. These three muffler systems have similar characters in some areas of the powerband, but also have enough differences in which you can make a decision based on what type of power you want from your Honda.

Fun Fact: I tested these mufflers on the 2020 Honda CRF450R as well as the 2020 Honda CRF450RWE just to see if the ported head, that the RWE comes with, would change the way each muffler delivered its power. After going back and forth on each machine, the character of each muffler system was the same on the stock cylinder head as it was on the hand ported Works Edition head. The description/results below is accurate for both machines.

FMF 4.1 RCT Muffler System:

The FMF 4.1 muffler system has more bottom end and throttle response than the other two muffler systems in this class. The Honda doesn't necessarily need more bottom end, but the way the FMF system delivers its power can give the rider some added freedom when trying to ride third gear through corners. The bottom end comes on strong and the Honda keeps its exciting, crisp RPM response feeling, but lets you run third gear through corners more than the stock, Yoshimura and Akrapovic muffler systems can. Using second with the FMF system almost makes the Honda a little too much too handle (on roll on) through very tight corners. When going to the FMF 4.1 system I reverted back to map 2 (mellow map) instead of map 1 (standard map) and ran 14/52 gearing. By using map one and going to this gearing ratio, it helped calm the Honda’s chassis down in second gear a little, but still kept its fun natured, snappy engine character. Mid range is broader and pulls farther than the stock muffler, but isn't as good as the Yoshimura system in this area. Up on top end the FMF system almost mimics the Yosh in pulling power feeling on the track with maybe slightly less over-rev than the Yosh system. What I like about the FMF muffler system is that it allows the rider to ride a gear higher in some areas of the track and rewards riders that like to lug their bikes more. The Honda in stock form is not the best lugging machine, but with the FMF system it gives the red bike more of a lazy man’s type of feel by allowing me to use third gear more. The FMF system is louder than the Yoshimura or Akrapovic systems by quite a bit even with the inserts in, but keeps that racey deeper sound. 

The good news is that the muffler packing has lasted longer than I expected. We are over the 12 hour mark on the 4.1’s and they still sound good. I used to get only 8-10 hours on other single FMF muffler systems, but these duals have proved to be more durable. 

Yoshimura RS-9 Muffler System With Works Edition Headpipe: 

Once installed and on the track the Honda’s exhaust note turned from high pitch 250F’esq to a deep throaty more traditional 450 factory race bike sound. The crack of the throttle (or RPM response) is slightly smoother and less crisp than the stock or FMF systems, but to me this is a good thing for the Honda chassis. Rolling out of corners, while in second gear, the Honda feels like it has more traction than the FMF and was more controllable while accelerating out of hard pack corners. The slightly smoother RPM response takes away the Honda’s excitement feel ever so slightly, but helps you gain a little more control coming out of corners. The mid range pull is healthier than stock, but with the Yoshimura system you will not be able to pull third gear through tight corners as well as you can with the FMF system. The Yoshimura system is very controlled and has more mid range torque than any other muffler in this test. Even though the Yoshimura system doesn't have that bottom end throttle response like the FMF system the recovery is still very good. With just the flick of the clutch lever (in third gear) the Honda will be in the meat of the power once again and you will be down the straight in a hurry. I noticed top end and over-rev was as good as stock (which is great), but not as good as the Akrapovic. To me the Yoshimura system is like the YZ450F of the muffler world. It does everything “pretty well” and gives you more rear wheel consistency that the Honda needs. You could tell Yoshimura was focused on smoothing out the bottom to mid-range pulling power when they designed this muffler system and they succeeded in doing so. It is also impressive that they didn’t lose any top end/over-rev in the process and gain a little more control.

The muffler packing that the Yoshimura RS-9 mufflers come with is superb and will last you longer than any other packing in this group. Yoshimura also offers the customer refurbishing, just in case you don’t want to DIY. The stickers on the mufflers themselves also last longer and will not turn color as fast as the others in this group.  

Akrapovic Evolution Muffler System:

Once I swapped to the Akrapovic Evolution muffler system, I could immediately tell this system helped the Honda chassis calm down the most. 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 any other system in this test. 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 FMF or Yoshimura. This type of character can allow you to use second gear in corners more because that second gear hit is not as abrupt or quick, so that doesn't upset your technique or the chassis. The Akrapovic also allows the rider to shift later out of corners and that means second gear is more usable 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. I ran the 14/52 gearing with this muffler system but decided on going back to the stock 13/49 gearing in order t get some mid range recovery back. The Akrapovic doesn't have the the bottom or mid range throttle response like the FMF or Yoshimura systems so this can give the Honda a slightly heavier feel on tighter tracks. The Honda has so much power to work with that a little less “hit” as well as “recovery” can actually help on faster/flowier tracks, but can also make it slightly heavier feeling than the other two mufflers when moving the Honda side to side. I really like that the Akrapovic system relaxes the engine as well off throttle and provides the CRF450R with less engine braking. This really comes into play on tracks with hard pack chop and small de-cel bumps.

The sound/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 on higher rpm’s, but just not that raspy high pitch tone of the stock muffler. I preferred the quiet inserts left in because it created more back pressure and gave me more traction at the rear wheel (out of corners) in all three engine modes. 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 muffler packing has proved to be durable but the stickers on the mufflers turn color quickly and get blown off.

Overall: I always let people know if you have no problems with your stock muffler system and like the way your Honda runs then by all accounts you can disregard this test. Just because I test something here doesn’t mean you absolutely 100% NEED it! If you’re in the market for a muffler system, have some extra money and want to know which direction to go then study up! If you want to alter or change your Honda’s engine character slightly, this test can help you decide on which direction you want to go. To me all of these systems in this test are better than the stock system because it helps the Honda’s chassis in one way or the other and offer spark arrestor inserts for the off-road guy. The Honda doesn't need more power as much as it needs a broader more forgiving connection to the rear wheel. These systems help the Honda in this area. 

Breaking The Systems Down:

Bottom End: FMF

Mid Range: Yoshimura 

Top End: Akrapovic

Over-Rev: Akrapovic

Low RPM Response: FMF

Mid RPM Response: FMF

Top RPM Response: Yoshimura

Controllability/Connection: Akrapovic

Weight: 

FMF: 8.5 lbs.

Yoshimura: 8.4 lbs.

Akrapovic: 8.4 lbs.

Sound/DB:

FMF: 121.1 DB

Yoshimura: 116.8 DB

Akrapovic: 116.1 DB

Pricing: 

FMF: $1499.99 www.fmfracing.com 

Yoshimura: $1499.99 www.yoshimura-rd.com 

Akrapovic: $1549.99 www.akrapovic.com 

If you have any questions about this test, please feel free to email me at kris@keeferinctesting.com. I am here to help if needed!

RIDE ENGINEERING 2018-2020 Suzuki RM-Z 450 Performance Link

By Dallas Dunn:

I’ve been helping out Keefer with photography content for some time now, but I’ve been wanting to get more into the testing side of things so Kris has gave me the opportunity to ride the 2020 Suzuki RM-Z450 test bike for the year, so the first mod for this bike was going to be the Ride Engineering 1mm longer lowering link. I wanted to give you a normal everyday blue collar perspective. I am by no means a professional test rider, in fact I am a heavy equipment operator that likes to ride his dirt bike. So if you can relate to that and have a RM-Z450, maybe you can relate to this test as well.

Simply installing the Ride Engineering link helped balance the RM-Z out on de-cel. If you’re running the stock suspension (valving/springs) this simple mod will help the RM-Z from wanting to transfer its weight towards the front end. The RM-Z450’s BFRC shock is known for unloading on de-cel (or riding high off throttle) and that can cause oversteer (knifing) on entrances of corners. Once you install the longer Ride Engineering link arms on the Suzuki it will settle down on de-cel and not pitch towards the front end as much. I noticed right away the bike felt more predictable and compliant coming into choppy braking bumps while keeping the rear end planted with less diving on de-cel. It gave me more sense of predictability and control when entering corners compared to the stock setup. Having comfort and predictability are things I look for when trying to improve my speed and technique. Running the sag at 107mm (fork height 4-5mm) with the link arm will alleviate some of your balance issues on the #RMaRMy. 

This Ride Engineering link Retails for $219.99 at www.ride-engineering.com.

You can use the code Keefer-20 to save some dough as well.

FMF 4.1 Full System Vs. Akrapovic Evolution Full System Vs. Akrapovic Slip On

We recently received the 2020.5 KTM 450 SX-F Factory Edition and after dissecting it for a few weeks, we thought we would test a couple different muffler systems on it. We wanted to see if we could improve upon the KTM Factory Edition’s delivery. The KTM comes with an Akrapovic slip on we thought since we have never tried one of their full systems, we would give that a go as well as an FMF 4.1 RCT full system to see how each compares to the standard Factory Edition set up. Just in case you were wondering, we also compared each muffler to one other and give you a breakdown of each category below. 

FMF 4.1 RCT Full System ($1049.00):

With the FMF system installed you will not be getting increased bottom end pull on the KTM, but you will be getting a little more bottom and mid-range RPM response (or throttle crack for you newbies). I noticed the added RPM response more out of corners (versus the Akrapovic) and the FMF system makes the KTM engine character slightly more free-feeling and exciting. I also appreciate that I am not getting any added de-cel popping (or lean sensation) with the FMF system. The KTM ran just as clean with the FMF system on then it did with the stock muffler. Where you will notice the most improvement with the FMF system is through the mid-range. The mid-range “meat” you will get out of the FMF 4.1 system is downright impressive. Rolling the throttle on out of corners and accelerating you will notice an increased pulling power that wasn't there with the stock muffler. 

Whether you're coming out of a corner in second or third gear, you will notice some extra torque feel getting to the next obstacle. With the added mid-range meat of the FMF system it really helped some of the gearing issues I had on tighter, less flowy tracks I tested at. Gaining some mid-range let me use third gear in some corners that I wasn’t able to with the stock system. With the stock system I would roll into these corners in second gear and have the right amount of "pop" to get me out quick, but I had to shift early once exited, to keep the rear wheel from spinning. Third gear was too tall of a gear to get me out of the corner quick, but provided less wheel spin on the exit. It was always a struggle for me to decide on which gear to use when being pressured from behind, by another rider. 

With the FMF installed I could easily use third gear and have enough "pop" to get me out of the corner in a hurry, yet it kept the wheel spin to a minimum by being able to use a taller gear. The FMF’s 4.1 system made me think less and twist the throttle harder, something I like doing. I didn't get any more top-end with the FMF installed, yet it didn't take any away from the orange machine. I did notice slightly less over-rev with the FMF system (from stock) when I got lazy.

Akrapovic Evolution Full Muffler System ($1299.99):

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 FE 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 and the muffler pitch is so quiet 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 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 450 SX-F Factory Edition 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. 

Top end and over-rev is where this Akrapovic Evolution system shines. Adding top end and over-rev to the already very capable Factory Edition 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 a swapped to an aftermarket ignition. 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.

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.

Akrapovic Vs. FMF:

Below are your typical engine categories and which muffler is best in what area. 

Bottom End: FMF

Mid-Range: FMF

Top End: Akrapovic

Over-Rev: Akrapovic 

RPM Response: FMF

Rear Wheel Connection: Akrapovic

Weight: (Akrapovic 6.2 lbs.) (FMF 6.9 lbs.) (Standard FE 8.1 lbs.)

Which One Should You Purchase?

If you’re looking for more bottom end excitement or rpm response look towards the FMF system. If you’re looking for the lightest muffler available and want more top end/over-rev you will love the Akrapovic. Cost is also a factor to me, so if I am looking at the most bang for my buck, the FMF is less money and I’m getting a good performance gain compared to the standard Akrapovic slip on that comes on the FE. The FMF muffler stands up to more abuse as the Akrapovic can look hammered quicker. That being said I was super impressed with the connection that the Akrapovic had on dry/slick tracks, so depending on what conditions you ride could be a factor in your purchasing decision as well.

Pro Circuit Link Arm (2020 Yamaha YZ450F)

I have tried links in the past on previous generation YZ450F’s with less than stellar results, but since Yamaha changed the frame on the 2020 machine, I thought I would revisit a link to see if it helps improves the Yamaha’s feel around the track. 

Pro Circuit's linkage arms are CNC-machined from billet aluminum and are designed to stiffen up the initial linkage curve in order to try and improve the geometry of the YZ450F’s chassis, in order to try and make the bike more stable in certain areas of the track. The linkage arms includes all of the required bearings and seals and is ready to bolt up. I wanted to see how it worked with the stock YZ450F suspension valving, so since Pro Circuit is backordered on them for a while, I purchased the Pro Circuit linkage arm at rockymountainatvmc.com for $189.95 . Once I received the PC link, I went to a few tracks to try the it and the stock link, back to back , to see if the Pro Circuit link is a benefit to the average rider. 

One thing that I want from the stock 2020 Yamaha YZ450F is less movement from the rear end under acceleration. With the stock link, the rear end can squat  too much at times (under throttle) and give me the feeling of less connection to the rear wheel under load. I do think the new 2020 frame and suspension valving has helped de-cel pitching, but once the fork is broke in, it can dive a little too much under hard braking. 

After I installed the PC link I re-checked my sag numbers to make sure they were in the spec I desired. I ran 105mm of sag with the stock link and am currently at 105mm of sag with the PC link. With the PC 143.5mm link installed (142.0mm is stock) the Yamaha has a noticeably different feel to it on the track. I immediately noticed that my rear end felt firmer under acceleration, but that feeling wasn't such a positive change. I went back to the van and turned my high speed compression (on the shock) out a quarter turn to help soften up the feeling on acceleration chop. Once I adjusted the high speed compression, I could start to feel the benefits of the Pro Circuit pull rods. 

Off throttle (de-cel) the Yamaha YZ450F felt flatter and less front end heavy, which gave me a YZ450F that now had more control on braking bumps. Corner entry wasn't improved, but I could feel how the Yamaha could lean over better through the middle to end of each corner. With the Pro Circuit link It took slightly less effort for me to continue my lean on the Yamaha, which usually isn't its strong point. Out of the corner (with the softer high speed compression setting) the Yamaha had more rear wheel traction and followed the ground better on acceleration bumps. The rear of the bike was higher in its stroke with the PC rods and gave me more of a plush feel than the stock link. I am able to run a softer high speed compression setting as well as low speed to get more comfort on choppy ruts. 

The overall feeling of the YZ450F with the PC link is a slightly calmer chassis off throttle with a better mid to exit cornering feel. If I had to point out a negative about the PC link it would have to be that once you’re off throttle the Yamaha has a firmer rear end feel. Even though I am gaining control on braking bumps, the YZ450F will feel firmer if the rider isn’t aggressive or pushing the bike. I feel the Pro Circuit linkage arms reward a more aggressive rider, so if you’re the average weekend warrior that likes to cruise his Yamaha YZ450F and is comfortable with your set up, these Pro Circuit linkage arms may not be the best purchasing decision. However, if you’re looking for more control on braking bumps, with a firmer feel and an easier area 2 to 3 (see testing term explanation below)  through corners, then the Pro Circuit linkage arms make a positive difference. 

Cornering Testing Terminology: 

Area 1: Beginning of corner (initial lean, tip in)

Area 2: Middle of corner (weight feel, traction, cornering stability)

Area 3: Exit of corner (rear wheel traction/connection, comfort)