Tested: FMF Factory 4.1 RCT Full System 1

As opposed to the stock two piece system, the Factory 4.1 RCT Full System comes in three different pieces.

How important is it to put an aftermarket exhaust system on your new scoot? Well, that depends on a few factors. Probably the biggest is the size of your bike. If you are running a 250F, or a 125 or 250 two-stroke (gasp!), you’ll need every advantage you can get, and an aftermarket system can go a long way. However, the bigger the engine, the more ponies your bike is inherently pumping out, so maximizing the manner in which said ponies are released becomes less important, especially in motocross racing.

99.9 percent of riders out there do not use a motor or bike to its full potential, which is one of the reasons why a really good 125 rider can blow by a weekend warrior on a 450 as if he were sitting still. Getting the power to the ground and using momentum is the name of the game, which in moto means having usable power rather than raw brute force.

So, on 450s, while there can still be horsepower gains, having that power in the right place is more important when look for the right pipe to purchase. And then there’s the whole bling factor thing.

After using the stock 2013 KX450F pipe for a while, we decided to give the FMF Factory 4.1 RCT Anodized Full System with a very bling worthy carbon end cap.


  • Available in Natural or Anodized Titanium muffler
  • Power gains throughout the RPM range.
  • Quieter than stock
  • Weight savings
  • RTS (Rapid Tuning System) makes for easy sound insert changes as well as adding US Forestry Approved Spark Arrestor.
  • Proprietary blend of alloy titanium made especially to our standards.
  • Can be used with FMF header or stock.
  • MSRP: Starting at $899.00

The FMF system mounts perfectly on the 2013 Kawasaki KX450F.

If you have ever used or been around a stock KX450F, you know that they are definitely not one of the quieter stock bikes out there, in fact they’re just the opposite. But having a loud machine doesn’t necessarily means it is producing more power.

Granted, with programmable ignition mapping on modern fuel injected machines, one can completely change the power characteristics of a bike without so much as lifting a t-handle, especially on bikes like the 2013 KX450F and RM-Z450 with their changeable mapping couplers. Nevertheless, it doesn’t hurt to change the exhaust system as well, and we found the FMF Factory 4.1 RCT to be a great option.

Machined fittings like the muffler mounting bracket are a testament to FMF's quality construction.

Just as advertised, the FMF system helped increase the power output “through the RPM range”, regardless of the mapping settings we had at the time. The KX450F in particular already has a good, torquey hit off the bottom, and the Factory 4.1 seemed to give that extra umph, that carried into the mid and upper ranges. If that wasn’t enough, both the sound reduction and weight savings were significant, thanks to the RCT (Resonance Chamber Technology) and titanium construction. And, of course, the FMF system is one of the best looking pipes on the market, so if you can’t beat your buddy on the track, at least you’ll own him in the pits.

If you are looking for a quality exhaust system that comes in well under a grand, the FMF Factory 4.1 RCT Anodized Full System might be the right choice for you. Solid power gains, weight savings (always a plus with today’s monstrous four-strokes), and noticeable sound reduction…all good things. What’s more? It's made right here in the good ol’ U.S. of A.

For more information, visit www.fmfracing.com



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