Power

FMF Factory 4.1 Slip-On (2019 Yamaha YZ450FX)

Story By: Michael Allen

The simple fact that more manufacturers are offering off-road closed course competition bike’s brings a smile to my face since at heart I’m an off-road lover. That being said I feel like most manufacturers should know that 99% of all off-road racing organizations require race bikes to be equipped with a spark arrestor. Although the bikes are really good in stock trim, this issue has opened up a nice market for aftermarket exhaust manufacturers to be able to come in and save the day while making bikes race legal. I recently ran into this issue when I decided to race our 2019 Yamaha YZ 450FX at a local District 37 Sprint Enduro and realized last minute that I needed a legal muffler. I made a couple calls, but before I knew it FMF saved the day and I had a slip on Factory 4.1 on its way (two days before heading to the race). 

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When I got the new 4.1 slip on muffler I immediately installed it, which was very self-explanatory and the fit and finish of the stainless can mated to the carbon endcap was top notch. Now here is the part of the story where Kris gave me crap about the spark arrestor… Admittedly I was putting on the muffler last minute and rushing to get all of my stuff ready to race the next day and I did what everyone says not to do; I assumed…. I assumed that the muffler came from FMF with the spark arrestor screen already installed, so I didn’t even think twice before loading up my bike and heading to the race. Well… I soon found out (thanks to my friend Brendon) that I didn’t have a spark arrestor because as Kris warned me about (and I forgot) FMF puts the insert in the bottom of the muffler box, where it stayed in my recycle bin until I got home that night. Luckily I was able to squeak through sound and spark arrestor testing and go to the start line. 

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Initially what I noticed when I fired the 450FX up was that the new muffler was slightly louder (without the screen insert) than the stock muffler. This slightly louder sound was deeper than the somewhat raspy sounding stock muffler. The performance of the stock muffler was by no means hampering the 450FX power character, in fact it was quite good, but like I said, I needed a spark arrestor. The new 4.1 has a larger opening than the stock muffler, which in turn gives the 450FX slightly less back pressure. With a little less back pressure the FX lost a touch of smoothness in the very bottom end, giving the bike a more on/off feel. The tradeoff for the on/off feeling on the other hand was that the bike gained some over-rev and seemed to pull slightly longer into the RPM range. During the race I changed maps to try and smooth out the bottom end which helped, but didn’t completely remedy the bottom end touchiness. After getting home, going into my recycle bin (thankful the trash man didn’t come) and installing the spark arrestor insert, the bottom end delivery smoothed back out. With the insert comes a quieter sound, which was welcomed as well as some added back pressure. The back pressure gives this bike a little more lugability without wanting to flame out, so I didn’t have to worry as much about covering the clutch in tighter sections of the trail. 

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The bottom line is that all bikes marketed to off-road racers should come with spark arrestor inserts, they don’t. That being said, FMF has done a great job at providing the off-road community a multitude of choices for whatever their specific type of riding entails. From full titanium systems, to more affordable aluminum slip on mufflers, FMF seems to have all the bases covered. At $449.99 for the stainless/carbon slip on that I installed, I think it’s a good combination of not breaking the bank while still looking slick at the track (not to mention that it takes almost two full pounds off your bike). If you have any  questions, or just want to tell me I’m a dumbass for not seeing the spark arrestor in the box, feel free to reach out to me at Michael@keeferinctesting.com . 

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.

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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. 

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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.   

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 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. 

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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.

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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. 

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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.

   

Yoshimura RS-9T Titanium Signature Muffler System For The 2019 Honda CRF450R

If there is one 2019 450 motocross machine that I think has the fastest overall engine character, it would have to be the Honda CRF450R. This engine is basically a race engine out of the crate. If you want to get to point A to point B in a quick manner, this Honda is the engine for you. So why on earth would you need more power? To me you wouldn’t need MORE, but maybe you can massage that power and move it around so that the engine delivery is slightly more controllable. This is where the KTM and Yamaha engines are better than the red machine. Both have more controlled power when the track gets rough or slippery. Controlled power is crucial in today’s 450cc world and a good muffler system can give you exactly this, if it’s a good system. Key word here people is “IF” it’s a good system. It is not as simple as reading dyno charts and slapping it on your bike. It requires real world track testing to feel the power character as well. We wanted to install/test a muffler system on our 2019 Honda CRF450R (that we purchased ourselves) to see if we could improve on a power plant that was already pretty damn impressive. We chose the Yoshimura RS-9 full titanium muffler system to try back to back with the stock system to see if it was in fact, what we were looking for.

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 When we originally tested the 2017-2018 CRF450R Yoshimura RS-9 system, we thought it was a pretty damn good system that was better than stock. However, the 2019 CRF450R stock exhaust changed for the better, so Yoshimura went to work on a new headpipe design to try and achieve even more power (than the stock 2019 exhaust system). Yoshimura also wanted to tuck in the new headpipe design, so it was less susceptible to crashes.

 Once installed and on the track the Honda’s exhaust note turned from the high pitch semi raspy stock sound 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 that of the stock system, but bottom end pulling power is increased over stock. Rolling out of corners, in second or third gear lets the rear wheel find increased traction over stock and was more controllable while accelerating out of hard pack corners. The slightly smoother RPM response takes away the Honda’s exciting feel slightly, but helps you gain a little more control coming out of corners. This is what I was looking for in a Honda CRF450R muffler! The mid range pull is healthier, with more meat, than stock and while the stock system had a tough time pulling third gear in tight/slower corners (without a gearing change), the Yoshimura system will give you an easier time rolling third gear in those tighter corners. With just the flick of the clutch lever (in third gear) the Honda will be in the meat of the power once again and have you down the straight in a hurry. We noticed top end and over-rev was better than stock, as the Yoshimura system helps the Honda carry second and third gears longer. It pulls amazingly well on deeply tilled dirt in second and third gear and there wasn’t a time where I thought to myself  “I need more top end pulling power”. You could tell Yoshimura was focused on controlling, yet increasing, the bottom to mid-range pulling power when they designed this 2019 CRF450R muffler system and they succeeded in doing so. It’s also impressive that they didn’t lose any top end and over-rev in the process, in fact they got some extra!

Craftsmanship is second to none with the Yoshimura RS-9 titanium mufflers.

Craftsmanship is second to none with the Yoshimura RS-9 titanium mufflers.

After weighing both the stock and Yoshimura RS-9T systems you will be saving almost two full pounds, which is great since the Honda is on the heavier side (on paper) for a 450cc motocross motorcycle. This is a significant weight loss but for $1,499.00 it is a very pricey bolt on modification. If you are looking to save a little money, Yoshimura offers the stainless steel/carbon version for $980.00, but you will not be saving much weight (only half a pound). 

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Again you can’t say enough about the craftsmanship that goes into a Yoshimura system. The welds are flawless and the mufflers tuck up inside the side number plates for a stealthy, compact look. If you’re looking for a little added pulling power, with more control/connection on the track, and not to mention sexiness out your new 2019 Honda CRF450R, the Yoshimura RS-9T system will help you do all of those things very well. You will have to decide if you want to dip into your checking account to pay for these added features, but if you're in the market for a 2019 Honda CRF450R muffler, there is not a better system out there for this model. The Yoshimura system has held up great over my years of testing them and you can even send your system back for Yoshimura to re-furbish if you choose (for a fee of course). You can head over to Yoshimura-rd.com to get yours or call them at 800-634-9166.

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Brake Tech Cobra MX 270mm Front Rotor Product Review

 

It seems like a lot of guys purchase aftermarket front brake rotors for their new bikes, so I decided to throw my hat into the ring and see what all the fuss is about. I asked Keefer if I could try out an oversize brake rotor to test, just to see if I was able to feel a difference. I am just your typical blue collar electrician that loves to ride, but could use some more braking power on my 2018 Honda CRF450R. He graciously handed me the Brake Tech CobraMX 270mm front brake rotor to evaluate and the task began.

Brake Tech has been around for a while, but maybe you're not familiar with the brand? They have years of R&D in brake rotors and brake pads with most of their effort being on the street racing scene. Having great success with street bike rotors, Brake Tech turned their focus to the dirt. Their newest product being the Cobra MX front brake rotor and it shares a lot of similarities with their already established AXIS road race rotors. The AXIS road race rotor is a full-floating front rotor where the Cobra MX rotor is what Brake Tech calls a semi-floating front rotor. When it comes to rotors there are a couple different avenues you can pursue; a fixed rotor, which is a one piece rotor, a full-floating rotor, which is a two piece rotor mated together with ground down shims, which allows the outer rotor to flex. Semi-floating rotor’s like the Cobra MX use ground down shims and spring washers. This allows you to have more stability under braking like a fixed rotor yet have the benefits of a full-floating rotor. Being made of two metals is said to aid in warping under high heat as well as a lighter weight. The Brake Tech rotor is cryogenically treated along with being fully re-buildable. Also a nice bling feature is that you get your color choice on the bobbin rings as they come in color choices of red, blue, black and KTM orange.

 

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Just like a lot of you blue-collar guys out there I get super excited with any new part for my dirt bike, so as soon as I got the box, right to the garage I went to install the nice looking piece. Installation was very easy and if you can change a wheel on your bike, you can easily install this rotor. Just like “if you can dodge a wrench, you can dodge a ball” (Dodgeball The Movie quote in case you didn't know). You will use the stock bolts and other hardware to mount the new rotor and caliper bracket. You can use your stock brake pads, but Brake Tech does recommend using a set of Brake Tech’s Ferdo brake pads. As I set out for my first laps I immediately noticed that the lever had a firmer feel over the stock rotor. At first this was a feeling I was not too fond of as the stock set up is very grabby and makes it hard to modulate the braking power through corners. As I did my motos I began to feel more benefits of the new Brake Tech rotor (even with the firmer feel) as it was not quite as grabby when you first apply pressure to the lever. Where I really felt like the Brake Tech rotor shined was under heavy braking. As I ride my motos I tend to get a little excited from time to time and come in a tad too hot into some corners. Where the stock rotor would lack a little stopping power the Brake Tech unit had great stopping power at high speed. You didn’t have to pull the lever in quite as much to get the Honda stopped in a hurry. This gave me a little more confidence and did allow me to charge harder into corners. With the Brake Tech rotor (under heavy braking) I would give it a “3.5” on the “Keefer Testing Scale”over a baseline “3”

 

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I give Brake Tech kudos on the Cobra MX front brake rotor and give it a solid 3.5 on the Keefer scale (If you don’t know what the Keefer testing scale is head over to the “Keefer Tested Podcast” and listen to his “How to Test” episode in the archives). As a hard working laborer I like that the Brake Tech Cobra MX rotor is durable as well as re-buildable. This is money saver in the long run for us 9 to 5’ers because we actually have to save up our money for every upgrade to our trusty steeds. If you damage a part of your rotor send it to Brake Tech and they will rebuild your rotor (labor free) and you will only be forking out the money for the damaged parts that were replaced.

 

We tried the Brake Tech rotor in conjunction with the Ride Engineering Brake Caliper as well and found the front brake lever to be slightly less firm, but even more powerful under heavy braking. The front brake lever had more of a progressive pull to it with the RE Brake Caliper installed. Without the RE Brake Caliper installed the lever has a firmer feel to it as Matt Sirevaag explains in this test. Either one of these products (by themselves) will help braking power on your machine. You will just have decide on how much stopping power you need.  

We tried the Brake Tech rotor in conjunction with the Ride Engineering Brake Caliper as well and found the front brake lever to be slightly less firm, but even more powerful under heavy braking. The front brake lever had more of a progressive pull to it with the RE Brake Caliper installed. Without the RE Brake Caliper installed the lever has a firmer feel to it as Matt Sirevaag explains in this test. Either one of these products (by themselves) will help braking power on your machine. You will just have decide on how much stopping power you need.  

 

The Brake Tech Cobra MX rotor kit retails for $339.95 and the brake pads for $59.95. This price is on par with most oversized rotors on the market as I did some research before typing out this article. Brake Tech is another great option if you are in the market for more braking power. Head over to BrakeTech.com and check out their selection of brake rotors and pads. -Matt Sirevaag 205 Pound Novice (Full Time Electrician/Husband/Father/Dirt Bike Lover)

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

 

Ride Engineering Billet Front Brake Caliper

 

I feel one aspect of a bike’s performance that is often over looked is the brake system. Most of us including myself have over looked this area more times than not. Some of us typically will go buy a new or used bike, drop money on an exhaust, wheels, graphics and maybe even race fuel. After all when you spend almost ten grand on a new bike you think the brakes are top notch off the showroom floor right? Or in my case, feel that you are not fast enough to notice the benefits of an aftermarket brake system. When Ride Engineering sent us there Billet Front Brake Caliper and steel braided brake line I was excited to give it a go. I was anxious as I felt this was my chance to see if this would be money well spent, even for the average blue collar, nine to fiver like myself. Keefer was nice enough to let me test this part and I gave it a go to see if this is something I would want to spend my own hard earned money on. Maybe more importantly, would I even notice a difference? 

 

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 The Ride Engineering Billet Front Brake Caliper is born from billet aluminum. Being made from billet aluminum instead of cast as most stock/production calipers are made, gives the Ride Engineering unit a stronger, less flexible body. This helps with a more precise feel at the lever while riding. It also has larger pistons than the Nissin units (that comes stock on most Japanese bikes). The Ride Engineering Billet Front Brake Caliper also incorporates large fins to help dissipate heat and aid in cooling when hard on the brakes. It comes in black or a polished aluminum finish, utilizes the stock brake pads and hardware for your bike. Ride Engineering offers this caliper for most bikes that use Nissin units like Honda, Kawasaki, Yamaha and Suzuki. 

We tested the Ride Engineering billet front caliper on our 2018 Honda CRF450R test bike, which just so happens to be the same bike I own as well. Booya!!!!! When it arrived I was so excited that even after a long day at work, I rushed home and went right to the garage to install. Yes, I still get excited about new parts for my dirt bike even in my mid thirties. The Ride Engineering Caliper takes a little time to install as you need to attach your old brake line or you can purchase a steel braided line from Ride Engineering like we did. Bleeding is not as much of a hassle if you own a vacuum bleeder, but in my case, I don't have one, it’s a little more difficult because I have to call on the wife or kids to help me bleed, old school style.

 

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 My first test with the Ride Engineering Caliper and Steel Braided Brake Line was at a local moto track that I am very comfortable with. When hitting the track it took a couple laps to get the hang of the new found feeling at the lever. Upon my first on track assessment I honestly thought I had a slight mushy feel at the lever, but as I started to pick up the pace I was mistaken. The feel at the lever was not mushy or soft but a far more progressive feel. This made it a lot easier to modulate the braking power coming into corners. The stock set up has a very firm feel and at times the braking can feel very grabby. This always made me feel uneasy, scared to cover the front brake (while in a corner) and especially in any sort of deep rut. I felt like I would almost lock up the front brake if there were any rocks, bumps or any inconsistency within the rut. The Billet Front Brake Caliper and its progressive feel at the lever gave me much more confidence everywhere on the track. Now I was able to modulate the braking as well as keep my finger on the lever throughout the whole corner without it being to grabby. This helped keep the Honda’s front tire from lifting out of ruts, which happens often with me. Don’t for one second think that there is not a lot of stopping power to go along with this progressive feel. I never felt as if I was lacking braking power or wanted more front brake. The harder you pull in the lever the quicker you stop and you are able to tell that you have more braking power available over the stock caliper within a lap or two. I also noticed a more consistent lever pressure no matter how long my moto was. I had some fading with my stock front brake, but fading wasn't as apparent with the Ride unit. 

 

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As you can see even the everyday nine to fiver can benefit from some better braking. I was quite surprised at what I have learned in testing this product. This is definitely at the top of my “to buy” list behind hand guards (Sorry Keefer) when I save up my pennies to buy my next bike, which is soon! Shhhhhhhh. Don’t tell the wife! The Ride Engineering Billet Caliper retails for $399.95 and the steel braided brake line is $69.95. Add that up and that is less than an aftermarket exhaust, but yet actually lowered my lap times, increased my corner speed and added that cool factory look to my bike. It was a Win.Win. -Matthew Sirevaag, 200 lbs. Moto Novice, Full Time Electrician And Full Time Dirt Bike Lover

Akrapovic Evolution Titanium Muffler System (2018 Yamaha YZ450F)

 

You’ve heard me talk a lot about how stock muffler systems are pretty damn good right? Usually I say something like, “the stock 2018 Yamaha YZ450F muffler system is hard to beat”, but that quote doesn't stop me from trying to see if there is something better out there. I am a fan of MXGP’s and seeing the Akrapovic mufflers on the Yamaha’s of Romain Febvre and Jeremy Van Horebeek got me thinking I wanted to try one of these beautiful looking systems. After some scouring, I found a US connection and got one delivered to give it a test ride. 

 

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

 

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Out on the track the Akrapovic Evolution muffler has a deeper sound and is slightly quieter than the stock system. I started the test with the “TP map” installed inside the 2018 YZ450F (if you don’t know what the TP map is, email me at kris@keeferinctesting.com). Roll on power delivery was smoother out of corners with the Akrapovic and “TP 1.0 map” installed compared to the stock system and “TP 1.0 map”. I didn’t really like the smoother delivery and I wanted to get some bottom end delivery back, so I went to the TP 2.0 map. Doing this helped me get some of the RPM response and bottom pull that I wanted back from the Yamaha out of corners. If you feel like you want a smoother delivery or ride hard pack you may want to leave the “TP map 1.0” installed with the Akrapovic. The Akrapovic system really comes alive once out of the corner as the Yamaha starts pulling harder and longer than the stock system down straights. Second and third gears can be stretched longer by the rider and once the TP 2.0 map is installed back in the bike (with the Akrapovic) rolling third gear in corners is slightly easier on the rider as well (with 49 tooth rear sprocket). Over-rev is slightly better through each gear with the Akrapovic and the overall engine feels like it revs a little quicker. The Akrapovic also gave the Yamaha YZ450F a free-er feel and takes away a little engine braking sensation on de-cel. 

 

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In conclusion, I feel the Akrapovic Evolution muffler system is an excellent system once going back to the TP 2.0 Yamaha Power Tuner setting. You will not be getting more bottom end than a stock system, but the gains through the mid-top end are a noticeable difference. It will be up to you if that difference is worth the $1300.00 you will spend on the Evolution titanium system.  Akropvic’s website is a very informative, clean, and one of the best aftermarket muffler websites to browse around on if you got the time. There are dyno charts, a sound tool that lets you compare the stock system to Akrapovic’s muffler sound, documents of replaceable parts, and technical data about the system itself. You can head over to akrapovic.com and punch in what bike you want to geek out on. I did, for about an hour! 

 

The Akrapovic accepts the use of Yamaha's stock heat shields.

The Akrapovic accepts the use of Yamaha's stock heat shields.

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

 

FMF 4.1 RCT Titanium Muffler With Mega Bomb Plus Headpipe

 

If you have kept up on my social media channels (@kkeefer120, @keeferinctesting) you will know that I have been riding the crap out of the 2018.5 Husqvarna FC450 Rockstar Edition and 2018.5 KTM 450 SX-F Factory Edition machines. I enjoy riding these two machines because they are easy to ride, well balanced and feel extremely lightweight when cornering. I do however wish they had some more RPM response and low-end excitement. Since the new Husqvarna RE’s and KTM FE’s are not coming with an aftermarket muffler this year I wanted to get my hands on FMF’s version as soon as possible to give you all some feedback, just in case you wanted to add some more bling and possible horsepower to your new machines.

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The new FMF 4.1 RCT Full Titanium Muffler System that you see here will fit on either your 2018.5 KTM Factory Edition or your Husqvarna Rockstar Edition. The FMF 4.1 system went on easy on both bikes and took only a few minutes to install. Thank you to Husqvarna and KTM for making the new bike much easier to change a muffler. Gone are the days of dropping the shock and cursing in the garage just so you could get your new muffler system on. I tested the FMF 4.1 muffler system at several tracks on both bikes and had similar results at each track I tested at. In stock form the KTM Factory Edition has a little more throttle response and bottom end pull than the Husqvarna Rockstar Edition, but the RE pulls slightly longer up top. 

 

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With the FMF system installed you will not be getting increased bottom end pull on either machine (compared to stock), but you will be getting a little more bottom and mid-range RPM response (or throttle crack for you not testing type readers). I noticed the added RPM response more on the Husqvarna, especially on low RPM, out of corners. The FMF system makes each machine’s 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 and both bikes ran just as clean with the FMF system on than 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 on either machine. Whether you're coming out of a corner in second or third gear you will notice some extra horsepower 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 at tighter, less flowy tracks I tested at. Gaining some mid-range let me use third gear in some corners that was tough for me to decipher which gear was better. 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, so 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. So basically what I am saying is that 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 either machine. I did notice slightly less over-rev with the FMF system (from stock) when I got lazy and tried to wring each machine’s neck out in second and third gear. I don't mind not gaining anymore top- end and losing a touch of over-rev with these two models, because they are one of the most powerful engines in these ranges. I am not looking to own a top fuel dragster here. 

 

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You have heard me say it time and time again that it's tough to beat a stock muffler system these days. You see more and more after market companies taking the time to release their new model systems because it’s not that simple to make a muffler system better than stock. FMF made their new 4.1 RCT titanium muffler with Mega Bomb Plus headpipe not only better through the mid-range, but a full pound lighter on the scales as well. If you just purchased your $10,000 plus Husqvarna RE or KTM FE and still have $1099.99 burning a hole in your pocket, I approve of this new system Lil D and the boys over at FMF developed. Head over to fmfracing.com or give them a call at (310) 631-4363 to see when this system will be available. 

 

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FMF Factory 4.1 RCT Full Muffler System Product Review

It’s hard sometimes to get more power out of newer four-stroke models nowadays with aftermarket mufflers systems. To be honest with you most stock systems are pretty damn good and aftermarket muffler companies like FMF work really hard to try and give you that little extra bit out of a system. I can sit here and tell you that FMF is one company (of only a couple in existence) that will take the time to listen to the proper feedback (either from me or other media testing outlets) and make the necessary changes to alter a new four-stroke machines power in the right direction. The key word here is “alter” and maybe not “gain”. Yes, in this article you will hear me talk about “gaining” a little pulling power, but to me the configuration of the 2018 Kawasaki KX450F FMF 4.1 RCT Muffler System power delivery is more “altered” from stock than anything. 

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The stock power of the Kawasaki is unchanged for 2018, but that doesn't mean it’s not a great bike. The engine has a snappy throttle response with a free feeling, on de-cel, without much engine braking. Once rolling on the throttle, the power is not as strong as the Honda or Yamaha, but still creates a lightweight feeling on the track. I didn't necessarily need more rpm response with the KX450F, but would like more meat through the mid to top end range. Bolting on the KX450F FMF Factory 4.1 system is bar far the easiest system I have bolted on for 2018. It took me literally two full songs on the Metallica Pandora station to change the muffler. The Kawasaki is a light bike stock, but I chose to go with the full titanium system that let me drop 1.8 pounds from the stock system! Visually the titanium FMF system is one of the most stunning aftermarket mufflers you can put on a bike. I love the blue anodized finish as it looks good on almost every make and model machine. 

 

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On the track the FMF 4.1 on the KX450F makes as much bottom end power delivery as stock and keeps that peppy/exciting RPM response. Where the FMF 4.1 system really impressed me was mid range pulling power when exiting corners. The stock system feels empty in this area, but the FMF fills the power-feeling in through the mid-range. What I mean by “fill the power in” is that the FMF system actually feels like it pulls as soon as you shift into third gear unlike the Kawasaki’s power where it feels like it lacks some pull through the mid-range. There is a dip in the Kawasaki’s mid to top end power and the FMF brings back some meat through that area, which in this case “fills in” that area. Top end is also increased slightly and you get increased pulling power near the end of each straight with the FMF. 

 

I did go back and forth with the couplers on the KX450F and came to the conclusion that although the lean coupler is better for bottom-mid range power, the standard coupler is slightly better from mid to top end. I will have to say when you do go to the lean coupler that the KX450F will pop more on de-cel with the FMF system than the stock muffler. With the standard coupler de-cel pop is minimal and not as noticeable with either system. 

 

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At the end of the day the FMF 4.1 RCT full muffler system is better than stock and that is not easy to do these days. It takes off some weight and looks better than the stock monstrosity. To me there is no negative with the FMF system and that is rare in an aftermarket muffler. I have tried other FMF mufflers, on some other models with some negatives, but the KX450F muffler is a good buy. Please note that re-packing of the FMF muffler is important for the can’s lifespan. The muffler portion (or can) will start to leave hot spots/scarring when the packing starts to burn out inside. Once you start seeing these “hot spot scars or markings” on the muffler, remove and re-pack is recommended. FMF sells re-packing kits and taking the can apart to re-pack is not that hard to do. I get around 10 hard engine hours (these are pro type hours) before I see these markings and have to re-pack. If you run it past the recommended time, you run the chance of hurting performance and damaging the core (or perf) inside the muffler. Kudos to FMF for building a good KX450F system and moving the power around slightly and gaining a little as well. If you have any questions about this test please email me at kris@keeferinctesting.com 

 

Bonus: If you listen to my Keefer Tested podcast you know that I rate some parts and motorcycles by a numeral system. I wanted to break down the FMF system to the stock system for you all below. If you don’t know what these numbers mean, please go listen to show #3 “How To Test” and you will understand better what these numbers mean. 

 

Stock/FMF:

Bottom End: 3/3

Mid-Range:  3/3.5

Top End:      3/3+

Over-Rev:    3/3+

Bottom End RPM Response:  3/3

Mid RPM Response:               3/3.5

Top End RPM Response:       3/3+