aftermarket exhaust

Has anyone found an aftermarket pipe that has resulted in a noticable increase in power and top speed?

if so, how much and where to get it from?


Yoshimura RS-3 Comp Series exhaust system has made a noticable difference in midrange and top end power on my '03 WR450f. Rocky Mountain ATV has the system for around $400.

Plan on adding a $70 James Dean jet kit to dial the carburation in.

I also got the Yoshimura TEC Kit which allows you to add a noise reducing insert. I run the 96 db insert and have not noticed a real loss of power.

With this set-up I have crisp throttle response, no back-fire, and cold starts with 2 or 3 kicks.

I can now run side by side wy my friends CRF450f and pass him once we hit 5th gear. I run a 14 tooth counter sprocket with a 48 tooth rear sprocket. Power wheelies in 4th gear at about 60mph with street 17" rims.

I went for the FMF Q series and found a big difference over the stock unit, wish I had done a year ago when I bought the bike. The unit is about $260.00. I believe also that the JD jetting is well worth it.

Thunder Alley ceramic coated. Increase in performance from bottom to top but way too loud. I think it was around $350. I have heard nothing but good about the Q and am thinking of going that way. :)


Hey Lowedog, Did you get the "quiet" insert? I have both and the quiet isnt that quiet, but it is better than the other one. The spark arrestor he uses is a weird one I havent seen before, its not a screen its fins that overlap eachother. Back on the subject, I noticed a nice gain with the thunder alley muffler and powerbomb header.


I added a fmf factory 4 to my bike for 700$ w/ the powerbomb header and i noticed a HUGE difference through out the entire powerband probally around a 8hp gain

Yea crusheddreams I got the "quiet" insert. I found it restrictive and difficult to jet. I ended up making my own insert. Same idea just bigger holes. It flows a lot better and does tone it down a bit. Even with the T.A. insert it is no where near 96db. The spark arrestor is differant. I think it is a Krizman (sp?). I also have a race core that I have never run. I have been told it will absolutly rip with the race core though. I will have to give it a try sometime.



I have run the race core quite a bit, its in it right now. The sound is very nice, deep rumble. I dont know if it adds much but it sure sounds like youre going fast. :)


I wanted the same thing a couple weeks ago and was told by some that for your money a stock YZ450F muffler would be the best bet. I've noticed alot better throttle response and has helped the mid and top range. Had to change main jet to a #175 and raise the needle a notch (5th from top). I'm not sure on HP gain. Unless money is burning a hole in your pocket you can find a used or practically new one on this or the YZ forum for less than $100.

dr.d can cure your ailments..

very nocticable power difference with a Q and pass sound tests as well. :)

Dr. D seemed logical since he has a very big presence in developement in 4 stroke Yamahas and mine works really well.As well it has a quiet insert that is available. I got mine for a great deal cause I know the guy that makes them. But I think that they are about $420.00 for the new D shape design.

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