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

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

Install:

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

On The Track:

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

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

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

Akrapovic Evolution Muffler System (2021-2022 Honda CRF450R)

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

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

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

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

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

Go to akrapovic.com to locate your nearest dealer. 

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

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

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

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

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

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

A couple of durability notes: 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

HGS Exhaust System For 2021 KTM 250 SX-F

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

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

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

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

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

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

DR.D Stainless Full Muffler System

By: Michael Allen And Kris Keefer

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

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

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

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

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

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

Keefer’s Notes: 

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

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. 

Akrapovic Evolution Muffler System (2020 Honda CRF450R)

This is embarrassing, but I am going to be completely honest here… I think about the Honda CRF450R a lot. More than other machines. I mean I will literally wake up in the middle of the night and think of things to test in order to try and make the Honda chassis calm down a little because I see so much potential in this bike, but I need it to be calmer. It turns incredible, has an insane amount of power, and has the best ergonomics of any bike, but it lacks some comfort and predictability to me at speed. This drives me crazy because I really like this damn bike a lot! 

I stumbled across the Akrapovic Evolution muffler system as I was doing some ECU mapping with Chad at XPR Motorsports on the CRF450R. Chad does the engines for the MotoConcepts/Bullfrog Spas Honda team and I noticed that they have been running Akrapovic systems on their bikes, so I asked if I could borrow one to see how it worked. Akrapovic's Evolution line is their full titanium muffler system and includes more in the complete package than other system that I have unwrapped. The welds are beautiful and to me the quality of the complete system is second to none. Installing the Akrapovic takes a little bit of finagling, but with some patience it does line up and fit well, as long as you leave most of the bolts loose when installing. Also included in the system are some extra parts, such as a carbon fiber guard, which protects the headpipe and resonance chamber from side impact. There’s also the hardware needed for the guard, along with some extra pipe springs and rubber grommets/spacers for the exhaust cans, as well as a set of quiet/spark arrestor inserts. Keep those in (more on that later). 

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

The pitch of the Akrapovic is ridiculously quiet when on the track and will almost give you that MXGP sound and feel. It still has that racey, crisp sound, but just not that raspy high pitch tone of the stock muffler. I 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. 

At just over 8 pounds the system will save you almost 1.5 pounds over stock and will set you back a whopping $1547.00! Is the cost worth it? I wouldn't go that far, but it is one of the better muffler systems that I have tried on the Honda CRF450R. If I was a Honda owner I would rather invest in a Vortex ECU, have it mapped, and save a few hundred bucks, because the Vortex ECU can do more to help the power character/chassis feel than that of the Akrapovic sytem. However, if you do have a deep pocket book and are going to get a muffler system anyway, this Akrapovic would be a great choice. It’s a beautiful system and works very well on a wide variety of terrain/tracks. 

Go to akrapovic.com to locate your nearest dealer. 

Yoshimura RS-4 SS/AL Full Muffler System For 2019 Kawasaki KX450

By: Dominic Cimino

Any of you that stay up to date with us here at Keefer Inc. are aware that I really enjoy riding the 2019 KX450. Like I really enjoy it. Maybe it is because we have the chassis and suspension dialed in just for me or maybe it’s just because the bike is so damn fun. Either way, I am excited to continue making improvements to this bike in the upcoming months because every time I ride it I feel faster. Next on the chopping block is the motor department and we decided to start with exhaust first. I wanted to test the RS-4 Stainless Steel Yoshimura system because I have had great luck in the past using their systems on other bikes and the guys over there always take great care of us. 

Yoshimura exhaust systems are made from scratch right here in Southern California. Their R&D facility houses everything from the race team shop, dyno/engine rooms, to the space where they lay all of their own carbon fiber. The attention to detail and quality of product is top notch in everything they produce and to give you a little more background on Yosh, you can watch this short clip:

https://www.youtube.com/watch?v=V5J5kltNfvQ

Although it is a couple years old and mainly showcases road racing disciplines, trust me when I say that it all translates equally into motocross. You can sleep peacefully knowing that your investment is going to be worth it. 

The stock exhaust system on the 2019 KX450 is not too bad overall. Beside it looking really bad (that is a no-contest) and weighing a decent amount, it produces a good tone and useable power. I think this exhaust compliments the motor and power delivery well by keeping things linear and quick revving - one of my favorite traits about this bike overall. But on the flip side, the motor does lack some “meat” in the RPM range and the over-rev tends to sign off relatively quickly at the top. Installation of the new Yosh was quick and easy with every single piece fitting in place perfectly. I love when that happens! The stainless/aluminum system that I tested weighed over a pound less than the stocker and comes in at a fair price of $675.78. In roughly ten minutes, the KX looked better instantly with the new system in place, and when I pushed the button to wake her up, she sounded healthier too. I am not a fan of obnoxiously loud exhaust systems so I was happy to listen to the Yosh when cracking the throttle on the stand. Definitely louder than stock, but not deafening. 

Before installing the new Yoshimura system, I did a couple morning motos at Glen Helen to get the best gauge of the stock comparison. The most obvious difference when cruising back onto the track was the tone, as it has a deeper/healthier sound. But when in stride, the exhaust made the KX come to life from the mid range and beyond. The linear power curve stayed true on delivery, but exemplified a more crisp powerful feel when on throttle. I felt the Yoshimura system was able to harness a little more “meat” that I have been searching for and also helped push the bike into the higher revs more efficiently. On the top end, over-rev was increased quite a bit as the KX seemed to pull longer and harder overall. I noticed when charging down Mt. Saint Helen I could hold 2nd gear almost half way down the hill before hitting the limiter. The stock exhaust would sign off way earlier than that in the beginning part of the day. I also realized I stayed in 2nd gear almost all the way around the Glen Helen circuit. This is a testament to the linear power I have been talking about on this 2019 KX450, and the Yoshimura system makes it even better. Where I didn’t notice a substantial improvement was bottom end power delivery. The KX is not a torquey bike in stock trim by any means, but I was expecting to get a little more bark with the new system. This was not the case and I found myself clutching the bike in the soft corners to wake it up in order to get back into the mid range, where I think it excels. 

Overall, the new Yoshimura exhaust system is a great performance improvement to this already great bike. Looks good, sounds good, and runs good - thats what it’s all about, right? Obviously, I am going to set my sights on continuing to improve the power delivery to round out this new KX450. I am happy with the mid/top end feel, so maybe we can experiment with new map settings to get a little more lovin’ down low.  As always, stay tuned for what is next here at Keefer Inc. If you have any questions about the 2019 KX450 please feel free to email me at dominic@keeferinctesting.com.  Or you can head over to Yoshimura-rd.com to see what they offer for your green machine.

Yoshimura RS-9T Full Titanium Sytem For 2019 Honda CRF250R

It’s no secret that the Honda CRF250R is still lacking some bottom to mid range power when compared to the other competitors in the 250 class in 2019. Seeing as how I’ve been logging some hours on this machine as of late, I decided to test the full Yoshimura RS-9T titanium system to see if we can get some added low end power. 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 curse words were thrown out in the garage while installing the Yoshimura exhaust.

Now to the part that everyone wants to know. Does the Yoshimura help the 2019 CRF250R? The simple answer is yes, but who likes simple answers? Not me! With the stock system, the Honda pulls nicely from mid top end, but when exiting corners and trying to grunt up obstacles, the engine needed some assistance. The best way I can explain the stock feeling 2019 CRF250R is that it needs help on “recovery" when the rider makes a mistake. “Recovery” basically means how long it takes the engine to recover by getting in the meat of the power again. When you're tired or lazy and miss a shift, this is where the Honda CRF250R gets smoked by the Yamaha YZ250F. I had to ride a gear lower at times in corners (with the stock CRF250R compared to other 2019 250F machines) and if I didn’t, it took a bit of clutch feathering and more coaxing to get the bike pulling hard again. If the track is flowy and fast the stock Honda works great, but when the track is tighter, this engine suffers.

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. I tested the stock system back to back with the Yoshimura system on consecutive days, so it was interesting to see the places (at 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 jump faces. 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 second gear and just use the meat of the newfound bottom end power to pull me up and over those types of jumps. When I had to be in second gear and scream the bike (with the stock system), I could now be in third gear and use the smoother/stronger part of the power to exit the turn with the Yoshimura muffler system. RPM response was improved as well and this made the Honda feel even lighter when popping out of corners. Connectivity to the rear wheel was improved and even with that extra RPM response I gained with the Yosh system, I received more rear wheel traction. From mid to top end I only noticed a sightly better pulling power down each straight with slightly more over-rev. This part of the muffler wasn't mind blowing, but took me a couple tracks to figure out that there was a little extra “meat” through the mid range (compared to stock). Overall the little Honda just has a little more RPM response, better pulling power through second and third gears, and a small gain when revving the bike out in each gear.   

 This doesn't mean that your new Honda CRF250R (with the Yoshimura exhaust) is going to be a YZ250F killer, but it closes the gap a little. If you have a 2019 Honda CRF250R and feel like you’d like a bit more bottom-mid range power I’d definitely look into the RS-9T system. There are three types of Yoshimura mufflers that you can choose from; a slip on muffler system ($763.15), the full stainless system ($947.36), and the full titanium system ($1463.15). Admittedly none of these are super inexpensive options, but it’s one of the few things in today’s four-stroke world that provides a true bolt on benefit. Besides, if you were looking to save a few bucks, I don't think you would be rocking a new 2019 Honda CRF250R right now anyway. 

Pro Circuit Ti-6 Pro Titanium Muffer System

The 2019 Yamaha YZ450F won the Keefer Inc. Testing shootout this year because it has all tangibles that are needed to let a rider go fast on the track with the least amount of work. I am a fan of the stock muffler system on the 2019 YZ450F, but was looking for a full system to help me lose some weight and gain a little more mid range pulling power without sacrificing low end delivery, that the stock system does so well. I went to Pro Circuit to seek out Mitch Payton and see if he would give me a Ti-6 Pro Titanium System to try out. I managed to walk out with a system, but missed out on the opportunity to speak with Mitch. He probably doesn't even know who the hell I am, but I appreciate that he got me a system to test out. I haven't tested that much Pro Circuit products in 2018, but our next couple project builds will have some PC products on board or 2019. 

The Pro Circuit Ti-6 Pro full system was created for professional racers competing in a series such as AMA Supercross or AMA Motocross to ensure they pass AMA/FIM sound regulations. The Ti-6 Pro Titanium Exhaust System is constructed of titanium throughout the head pipe, mid pipe, and canister while the end-cap is carbon fiber. I wanted the “Pro” system because I have learned that loud mufflers are not the best mufflers for power feeling on the track and sometimes putting an insert in “some” mufflers actually helps power delivery.

Installation of the PC system was painless to install (for Yamaha standards), but always make sure to install the headpipe on the cylinder head studs and then connect the mid pipe. Once the mid pipe is slipped onto the headpipe you can begin to tighten the headpipe nuts. This assures that the mid pipe doesn't bind and is free. 

So how does this sucker feel out on the track? The exhaust note on the Pro Circuit Ti-6 Pro is not near as loud or weird sounding as the Ti-6 or T6. The exhaust note on the “Pro” is deeper and slightly quieter, which I personally like more. The power delivery is slightly smoother down low, but only on throttle opening. At 0-5% throttle position there is a slightly softer RPM response, which I didn't mind on nasty, dry, choppy tracks in Southern California. If I needed more bottom I simply ran a more aggressive map and that helped the “pop” I was looking for out of corners. I usually ran the TP 2.0 map with the Pro Circuit system and it made me happy with the amount of smooth roll on power I had. The rear wheel definitely feels connected to my throttle hand and in comparison the PC system has more bottom end power than that of the Akrapovic that I tested a couple months ago. The mid-range is where I wanted more power out of the Yamaha and this is where exactly the PC system delivers. The meat of the Ti-6 Pro’s power out of corners and accelerating down the next straight is much better than stock. I am able to use second and third gears longer with the PC system (compared to stock) and even though the low RPM response is slightly softer than the stock system, the mid-range RPM response is much more instant. Mid- range RPM response is crisp and makes the Yamaha feel “lighter” when trying to hop over square edge choppy areas of the track when accelerating. Top end pulling power is as good as stock as the PC Ti-6 Pro doesn’t pull harder up top, but the PC system does have slightly more over-rev. I am able to be slightly lazier with my shifting and can decide to shift later after each corner. 

I was impressed how the Pro Circuit Ti-6 Pro delivered and spread out its power and to me made the Yamaha even more fun to ride. If that is possible? The PC Ti-6 Pro Titanium System runs $1,064.95 and is available over at procircuit.com. I will be doing a 2019 Yamaha YZ450F Muffler Shootout Podcast in the very near future, so if you want to hear how it stacks up against its competitors listen and subscribe to the Rocky Mountain ATV/MC Keefer Tested Podcast right now. 

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

Dubach Racing (DR.D) 2018 Yamaha YZ450F Slip-On Muffler

Before I start this review I am going to go on a little rant here, so bare with me. Mufflers are always a hot topic when it comes to horsepower, especially when you get a new bike. I know a lot of riders out there get a muffler system before they even ride their new bikes! Ride your new bike and break it in before purchasing any muffler please! See what you're working with and purchasing, so you know if its better than stock. Because if it’s not better than stock, what is the reason you purchased it in the first place? To look cool. To drop some weight. Those two statements would be the only answers that are acceptable when someone asks you why you have a new muffler on that bike that has an hour meter that reads 0.1 hours. Ok moving on…….. 

When it comes to Yamaha motorcycles, Doug Dubach is a name that comes to mind immediately right? Doug has been a Yamaha test rider for 87 years and is almost that old, but don't tell him I said that. Seriously, Doug knows the ins and outs of the 2018 YZ450F like the back of his hand, so I was anxious to try his slip-on muffler when I reached out to him. However, instead of trying a full system I wanted to do something different and just try a slip on muffler system. A slip on system is only the rear section that keeps the stock headpipe and mid-pipe intact. I installed the DR.D stainless muffler system (that saves just over one pound compared to stock) in only 3.5 minutes. 

I am very picky when it comes to mufflers and how they deliver the power to each bike I evaluate. The DR.D slip on keeps the stock feeling YZ450F bottom end pull intact, but maybe softens the low end RPM response just a tad. This is only noticeable on super loamy style tracks, but helped rear end traction feeling on hard pack style tracks. Losing a little RPM response and gaining some rear wheel traction is not a bad thing on this beast of an engine. I want to note how hard it is to build a muffler system that keeps the low end pulling power feeling of a stock 2018 YZ450F as I have tested several full muffler systems that had less bottom-end than stock. Where most of you will feel the difference between the stock muffler and the DR.D is mid range pulling power. The mid-range meat that the DR.D system delivers is impressive and gives you a better pull in second gear and helps the third gear transition when shifting. With the stock Yamaha system (with stock gearing) it was hard at times to carry third gear through corners, so shifting to third immediately after the corner was a must. With the DR.D system I have the freedom to leave the Yamaha in second through the corner and shift early without the blue machine falling off the power much. Or if you choose to run third gear in corners it picks up the power slightly earlier and helps lazier/lug heavy riders get out of the corner quicker with more rear wheel traction. Top end is also slightly increased over the stock muffler as you are able to hold each gear (well, to be honest the only gears I used was first through fourth) slightly longer. If you're looking for more over-rev this isn't the muffler you are looking for because the DR.D system keeps all of the stock feeling over-rev on the track and doesn't gain anything extra. This isn't a bad thing as the standard YZ450F power character revs out just fine. 

The DR.D slip on stainless system is the best slip on system that I have tried on the 2018 Yamaha YZ450F and will only set you back $395.00. Not to mention that you’re not losing any horsepower and gaining some mid-top end, while getting some added rear wheel traction. The DR.D muffler system comes with quality packing, has a nice sound to it without it being obnoxiously loud, is easy to re-pack on your own and doesn't blow out quickly. If it comes time to re-pack and you don't want to do it yourself, Dubach has an exhaust packing service where you can send in your muffler and he will re-furbish it for you for a small fee. If you're wife is having a conniption fit about you spending more money on your new bike you can tell her you're saving around $600.00 by not going to a full system. You’re actually compromising and doing her a favor! You're welcome fellas! You can check out all of the mufflers that DR.D makes over at dubachracing.com. 

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