FMF

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). 

IMG_3591.jpg

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. 

IMG_3594.jpg

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. 

IMG_3590.jpg

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 . 

FMF 4.1 RCT Titanium Muffler System (2019 Kawasaki KX450)

The 2019 Kawasaki KX450 is the most improved machine of the new year, hands down! It has a very responsive engine character, comfortable suspension, a lightweight feel and cornering that is very neutral. I will be the first one to admit that I get nervous about sticking on any type of aftermarket muffler system when I really like the stock power curve of any machine. Sometimes aftermarket mufflers are just smoke and mirrors. They are lighter, titanium, look cool, but in the end they are no better than your heavy, ugly, big stock muffler. While I was testing the 2019 KX 450 earlier this year I could hear this little voice inside my head say “it’s going to be tough to make a muffler that is better than this stock one”. Fast forward to a few weeks ago and a shiny new FMF 4.1 RCT titanium exhaust shows up at my door, to be evaluated on the green machine. I sat on it for a week knowing that this new, shiny, lightweight piece of FMF artwork might not be better than the current monstrosity that is on the 2019 KX450. Nonetheless I installed the FMF system (which was easy I may add) and headed to the track to give it a go. 

 

IMG_9952.jpg

 

The stock power curve of the 2019 KX450 engine has a snappy throttle response (with a free feel to it) and at times can almost be too much through corners with the standard green coupler installed. Once rolling on the throttle and passed the corner, the power is not quite as strong as the Honda or Yamaha, but still creates a easy to ride power feel on the track. I didn't necessarily need more rpm response with the 2019 KX450, but I wouldn’t mind some more meat through the mid to top end range. Bolting on the KX450 FMF Factory 4.1 RCT system is by far the easiest system I have installed on any 2019 machine. Installation literally took me through two full songs on the “Classic Rock” station on Pandora. Not bad! The 2019 Kawasaki is a light bike stock, but FMF sent me the full titanium system, which dropped the Kawasaki’s weight by 2.9 pounds from the stock system! To me the titanium FMF 4.1 system is one of the most stunning aftermarket mufflers you can put on any bike. I love the blue anodized finish as it looks good on almost every make and model machine there is.

 

FMF builds great looking mufflers! 

FMF builds great looking mufflers! 

 

On the track the FMF 4.1 makes a slightly smoother bottom end power delivery, but keeps that exciting RPM response. Where most of you will feel your hard earned money is in the mid range pulling power when exiting corners. The stock system feels empty in this area, but the FMF fills in the power through the mid-range. What I mean by “fill in the power” is that the FMF system actually feels like it is shooting forward, as soon as you shift into third gear, unlike the stock Kawasaki’s power where it lacks some “meat” through the mid-range. The FMF 4.1 increases that mid range area and gives the rider some more freedom to be lazier in third gear. That is great news for all you vet riders out there, trust me! Top end is also increased slightly and you get increased pulling power near the end of each straight with the FMF. Over-rev is slightly increased as well with the 4.1 (over the stock muffler) as I could leave the KX450 in second and third gear slightly longer. The one downside to me is that it is loud sounding (compared to the stock system). It has more of a deeper/throatier pitch to it, which makes it sound louder than the stocker. 

 

I tested couplers along with mapping with the Kawasaki R&D guys and came up with a couple options for you (see attached maps). The white coupler map is better for bottom-mid range power, but the black coupler map is slightly better from mid to top end (the black coupler map is what I am running now). The good news is, unlike last year, the 2019 KX450 FMF 4.1 system will not have that de-cel popping with either coupler (along with these installed maps), which is a huge plus when it comes to a clean ignition/fuel mapping power feel.

 

Black Coupler Fuel Map 

Black Coupler Fuel Map 

Black Coupler Ignition Map 

Black Coupler Ignition Map 

White Coupler Fuel Map 

White Coupler Fuel Map 

White Coupler Ignition Map

White Coupler Ignition Map

 

At the end of the day the FMF 4.1 RCT full titanium muffler system delivers a smoother roll on bottom end delivery with a mid to top end puling powerl that is better than stock (along with improved mid-top end RPM response). I will say this again….Being able to achieve a power delivery that is better than what an OEM muffler system can give you is very hard to do. FMF has achieved this with their 4.1 system on the 2019 KX450. Not only does it make power, but it also takes off some weight and looks better than the stock bazooka. I wanted some added control down low and more mid range (on the 2019 KX450) so with this FMF system I got what I was looking for. I am not going to sit here and tell you guys that every FMF system, for every machine is better than stock, but with this one they knocked it out of the park. Don't be scared to try the maps that are attached above, because with today's four-stroke technology, getting the correct mapping for a certain muffler can really make a difference. 

 

IMG_9967.jpg

 

Attention mechanically inclined riders!!!!! 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 away from inside. Once you start seeing these “hot spot/scars/markings” on the muffler, remove and re-pack it ASAP. FMF offers re-packing kits and taking the can apart to re-pack is not that hard to do. I get around 12 hard engine 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. Don’t be a dummy and waste your money, re-pack your muff! 

 

If you have any questions about this test please 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.

IMG_7820.jpg

 

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. 

 

IMG_7898.jpg

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. 

 

IMG_7818.jpg

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. 

 

IMG_7900.jpg

   

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. 

IMG_7283.jpg

 

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. 

 

IMG_7286.jpg

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. 

 

IMG_7288.jpg

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+