Bill’s Pipes is back in a big way, and their full line of RE13 exhaust systems is a great comeback effort.


BILL’S PIPES RE13 Stainless Steel/Aluminum Exhaust System

APPLICATION: All bikes (tested here on 2014 Kawasaki KX450F)

PRICE: $699.99


Bill’s Pipes is a name that should be very familiar to those who have spent any time racing two-stroke motocross bikes. Having built systems for 125cc National Champions Doug Henry, Steve Lamson and Travis Pastrana, as well as multi-time Arenacross Champion Buddy Antunez, the Corona, California-based shop is no stranger to racing at the highest level.

When four-strokes began to dominate the MX landscape nearly a decade ago, Bill’s Pipes seemed to be overshadowed by the dozens of new exhaust manufacturers who seemed to come out of the woodwork. In spite of fielding the original Rockstar Energy Suzuki team with Jason Lawrence, Mike Brown and Ryan Mills during Suzuki’s “strategic alliance” years with Kawasaki, Bill’s Pipes simply hasn’t been the same powerhouse in the four-stroke arena.

That, however, is about to change. The crew at Bill’s Pipes relaunched their MX effort recently with a complete line of four-stroke MX exhaust systems, including a full titanium system for those looking for an elite system.

We got our hands on a RE13 stainless steel/aluminum system for our 2014 Kawasaki KX450F test bike a couple weeks ago, and have spent several full days at a few different tracks, testing the system against the OEM exhaust.

The RE13 system from Bill’s Pipes fit perfectly on our 2014 Kawasaki KX450F test bike. The header pipe is tucked in well and was non-offensive to test riders’ boots or pant knees.


– The RE13 stainless steel/aluminum system fit perfectly, and installation was a breeze on our Kawasaki. No jiggling, wiggling, or cursing was required.

– During installation, we noticed that the header pipe mount is equipped with a rubber dampener to help absorb vibration and prevent breakage. A nice touch, indeed.

The RE13 muffler is equipped with several internal baffles that help keep the exhaust note low. The can has a unique shape and is tucked in nicely. The carbon fiber end cap is beautiful.

– The RE13 aluminum muffler is equipped with several internal baffles that help quiet the exhaust note. Overall, the system has a nice throaty sound, but is nearly as quiet as the stock system.

– The shape of the muffler allows it to be tucked away nicely, and it does not come into contact with the rear tire, even when we installed a wider 120/90-19 Dunlop.

Look closely and you’ll see a rubber dampener to help combat vibration damage to the mount. The TIG welds are nicely done, too!

– One of the Kawasaki KX450F’s strongest attributes is its amazing powerband. The Bill’s Pipes system enhances it everywhere, without robbing power from any single point in the rpm range. The KXF maintains its broad controllability, but when ridden aggressively is even more exciting with the RA13 installed.

– While other aftermarket systems hit harder in the middle and pull further up top at the expense of some low-end throttle response, the RA13 offers a noticeable boost in torque and mid-range, while at the same time maintaining the Kawasaki’s ability to rev out in each gear.

– The header pipe’s resonance chamber is tucked in nicely, up and out of the way of the rider’s boot. None of us burned our boots of pants on it, and this is rare for an aftermarket system with no heat guard.

– The TIG welds on the stainless steel header and mid-pipe are works of art.

– Spark arrestor screen included for our trail riding brethren.


– We’re nitpicking here, but the stock muffler bolt is far too long to use with the RA13 muffler. It would have been nice to include a shorter bolt.

– Not that we would run it, but it would be nice to have the option for a heat guard on the header pipe.


We are very happy with the performance gains that the Bill’s Pipes RE13 exhaust system coaxed out of our 2014 Kawasaki KX450F test bike. Affordably priced, the unit is of high quality and among the best-performing modifications we’ve tested on the big green bike. Thanks, Bill. It’s good to have you back!

The header pipe of the RE13 is nicely made, and tucked in even better than stock.