Exhaust Upgrades for 2017-21 EXC / FE KTM & Husky

Installation Instructions

The mufflers that come on the 2017 - 21 EXC's and FE's are indeed, totally different than the mufflers that came on the 2012-16 models.

We have therefore, made new muffler end caps for the 2017-21 models called the “Power End Caps”. The STE-2 caps for the 2012-16 bikes will not fit the 2017's and vice versa.

And the 2020 muffler’s are totally new, so the 2020 end caps won’t fit the 2017-19 bikes.

In 2020 the Husky and KTM started making the mufflers the same on the FE , the EXC-F and XCF-W bikes, so the same end caps works on all, which is nice

So let's answer one of the biggest questions we get asked all the time…

“What's better… this end cap or a whole new slip on muffler?”

Well the dyno graph below doesn't lie.


The the orange line is the power you get from the 4.1 muffler you see on the right, and the blue line is the power you get using our Power End Cap attached to a stock muffler.

This test was a 3rd gear run on a 2018 500 EXC, with our Big Bottom Kit and our Fuel Programmer.

On top of making the same power for less than half the price, it's even quieter with the Quiet Insert installed.

So we have no doubt that you'll make the intelligent choice here.

The biggest difference between the 2012-16 mufflers, and the 2017 -19 muffler shown below, is that the perforated core and the packing material now go all the way to the end of the muffler can.

On the 2012-16 mufflers, the muffler core stopped halfway through the can, making for an interesting muffler configuration that honestly worked great.  

The only reason it was changed, I suppose, was to get the noise output to meet the EPA requirements so you don't hurt the little newborn babies ( or golfers ) ears as you drive by. Either way, new muffler, new end cap

Any time you increase exhaust flow, as in using this end cap or any other aftermarket muffler, you make the bike run leaner. These bikes already run very lean and just increasing exhaust flow really puts you in the danger zone for engine damage.

When you install the Power End Cap, you must at least use our TPS Tuner or Fuel Programmer on 250’s and 350’s, and our Fuel Programmer on 450’s / 500’s / 501’s all size bikes to get the extra fuel to the engine. Everything is designed to be used with our Power Intake Tube.


This is the stock muffler tip below, which slides into the core of the muffler. You can see that the entrance to the exit tube, has a cover welded over it.

This means all the exhaust flow has to squeeze past it to get out through the screen along the sides, which is not a very effective design.


This screen is the spark arrestor, so you can’t just cut it off, because if you did you'd no longer have a functioning spark arrestor.

The image below is the exit of the stock muffler tip. It has not one perforated screen, but two.


The overall exit area is equal to a 1/2 inch (or 13mm) hole. Both the 450 and 500 have a piston diameter of 3.74 inches, so you need a more free flowing exhaust than a 1/2 inch hole, for a 3.74 inch bore.

You can't take all the pressure that the engine makes, especially from a 500 size piston, and not let it out of the exhaust.

All that pressure has to go somewhere if it can't get out, so it just backs up in the engine, where it turns to heat and kills performance.

Between the exhaust not getting out, and the already lean running engine, these things are on the verge of melting down the way they come from the factory.

The 2017-19 Power End Cap

The new Power End Cap is a modular design that:

1.  Gives you a forestry approved spark arrestor.

2.  Flows much more than the stock end cap, for a large increase in bottom to top end power.

3. Has an optional Quiet Insert that significantly reduces noise with minimal loss of flow - and can be taken in and out easily without affecting the spark arrestor.

4. Designed and shaped to not burn your stock turn signals.

This is the high flow, large area, non restrictive spark arrestor screen set up that we use below. It flows straight into the exit hole.


And this is the exit hole in our end cap. The hole diameter is 1.375 and only constricted for a 2" length on the 2017-19 end caps.

IMG_1882 (1).jpg

The spark arrestor is even in place, as you may be able to see through the light. Look how much it flows. This exit hole size is on par with any aftermarket slip on muffler.

The 2020 - 22 Power End Cap

On the new 2020-22 Power End Caps, the hole has an inner diameter of 1.5”, and the Quiet Insert that comes with the end cap, is 1.2" diameter. It knocks another 1.5 DB off the sound, so it's nice that it just comes with it for free

Power End Cap for 2017-19 FE in Black.jp