FMF Racing Stainless/Aluminum 4.1 RCT System with Megabomb Header for 2016 KX450F

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Tested: FMF Stainless/Aluminum 4.1 RCT with Megabomb Header for 2016 KX450F
Vital Review

As some readers may have noticed, I've mentioned spending quite a bit of time on the Kawasaki KX450Fs over the past few years, and they hold a special place in my heart. So to say the least, I was quite excited for the 2016 model to come out, due to its large revamp. Overall, I think almost every test rider will agree that it's better in about every aspect over its predecessor. For me though, I do have one area I missed a little from the '15 and prior model, the low-end snap. While the '16 model has plenty of torque, it doesn't have quite the same instant snap of the throttle that some of the earlier models had. While the rest of the engine is awesome, I wanted to wake it up just a bit, if possible. In this case, I decided to slap FMF's more affordable Stainless Steel/Aluminum full system, the 4.1 RCT with a Megabomb head-pipe to attempt the job.

FMF Stainless/Aluminum Factory 4.1 RCT System with Megabomb Header Features:

  • RTS (Rapid Tuning System) makes for easy sound insert changes as well as adding a US Forestry Approved spark arrestor.
  • Quieter than stock.
  • Exhaust can and mid-pipe can be used with FMF or stock head pipe.
  • MSRP $699.99 with Carbon Fiber end-cap.

First Impressions

As always, everything from FMF comes well-packaged. The exhaust can is shipped in a smaller box, while the Megabomb and mid-pipe are in sealed bags; along with a final bag that has any optional sound inserts (if they aren't already in the can), along with any additional hardware and some FMF stickers. Finally, it's all packaged with plenty of cushioning material in the box for shipping.

In this case, I chose to go with FMF's stainless/aluminum version of the 4.1 RCT to save some cash, but opted for the carbon fiber tip for the factory look. All-in-all, the pricing came out to $666.99, with $25 of that going towards the optional carbon fiber cap.


One of my favorite things about FMF's exhaust systems is the fit during installation. Once I took off the two-piece stock system, FMF's three-piece system slipped right together. The Megabomb header simply bolts onto to the stock cylinder head studs with two nuts and an exhaust flange, with the mid-pipe slipping on next and bolting to the subframe. FMF's mid-pipes don't have a solid thread inside the mid-pipe's mount section, but instead use a floating threaded nut on a small flange. This allows a bit of wiggle room, which is great considering I tend to lower the KXF subframes around 8mm. This means I don't have any issues with fitment, even though the mounting location on the subframe has moved down and slightly forward.

Beyond that, the 4.1 RCT muffler slips on last, with a solid aluminum bracket used to bolt it to the end of the subframe. The exhaust bracket is also slotted a bit, which once again makes fitment a breeze with my slightly lowered subframe. Between the mid-pipe and exhaust can, there's quite a bit of room for fitment if your subframe is tweaked as well. FMF provides a shorter bolt to replace the long shouldered unit that holds the exhaust can in place (due to the stock can being rubber-mounted), but I tend to still grab a longer bolt out of my stash. This is so I can run a locknut on the backside, to ensure I don't run into any problems down the road.

On the Track

As I stated early on, I was trying to gain back some of the initial snap that I felt was missing from the current KX450F. As I rolled onto the track the first time, I was quite hopeful as the bike felt more responsive when I blipped the throttle a few times.

After a few laps of warming up and I started coming out of the corners more aggressively, I felt exactly what I had been looking for. With the FMF system, the bike didn't feel too aggressive, but just seemed to make the power come on a bit stronger at a bit earlier point in the RPM range. This made using the clutch unnecessary when popping over obstacles out of corners, as the bike had the pull to do it by itself.

Once the bike got past the improved bottom-end power, the continued pull into and through the mid-range felt fairly similar to stock, as the Kawasaki already packs plenty of punch there. At about 8500rpm, the KX450F has a small drop in power for about 1000rpm, before pulling again and then finally dropping off (check out our dyno charts from the 2016 450 Shootout for a clear look at this). With the FMF system however, the KX450F feels like it continues to pull through this small lapse, before having a much more gradual sign-off. Between the extra bottom-end grunt and snap, along with the added power up top, the FMF system really helps the KX450F just feel a bit more complete and well-rounded.

Long­-Term Durability

I have no complaints regarding the durability of the exhaust in any way, and it still fits great after a few months, despite taking if on-and-off the bike a little over a dozen times. My one and only complaint lies with the header, which sticks out just far enough to burn the top corner of my boots from time-to-time. This also depends on which boots I wear, as some are constructed with more durable rubber or leather compounds in that area, but some have plastic which will melt from short-terms of contact (such as my Fox Instincts).

The Last Word

Once again, FMF's exhaust system has accomplished what I had hoped for, if not a little more. It produced gains on both ends of the power range, while being lighter and just flat out better-looking. If you're looking to shed even more weight, FMF's titanium systems are only $150-$200 more in this application. As for the price of this stainless system, it falls into the mid-to-higher range of where the top exhaust companies are. My only real complaint about the actual product itself was the slight burning issue I had with the head-pipe. However, FMF now sells a carbon fiber head-pipe heat shield, like some of the race teams have used, but it's an additional $99.

All-in-all, I love the fit and finish, the power, and the fact that the exhaust/mid-pipe can also be used as a slip-on system with your stock head-pipe if the FMF one gets damaged. However, I would like to see the stainless/aluminum system be a tad bit cheaper, as it doesn't take too much more to just pull the trigger on the full titanium system. Or maybe I should just give props to FMF for keeping their top-of-the-line systems a bit under their competition.

Vital MX Rating: 4 Stars - Excellent

Check out to see all the complete exhaust systems, or slip-ons for your motorcycle.

About the Test Rider

Michael Lindsay - is a born-and-raised moto freak and gearhead from the heart of motocross in Southern California. First swinging a leg over a bike at the age of five, he immediately caught the racing bug, spending nearly every weekend behind a gate…and a lot of time on the couch while injured. While swinging back and forth between moto and the off-road scene, giving him a wide range of experience on the bike. Of course, all of this led to one thing: Lindsay loves working on his bikes almost as much as he loves talking about them. When he’s not in the Vital MX forum or writing his latest product review, you can find him out at the track taking dirt naps, snapping some pictures, or drooling over the latest parts for his bike. With an outspoken personality, gearhead background, and as Vital MX’s guru for product, Michael is here to share his unbiased opinion.

Review and Photos by Michael Lindsay


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FMF Racing Stainless/Aluminum 4.1 RCT System with Megabomb Header for 2016 KX450F
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