08 YZ450F Silencer

Has anyone done any modifying to the stock silencer on the 08 450s? If so,did you have to do any jetting changes.My bike seems to have alot less power compared to friends 450s and they have aftermarket exhaust.The stock exhaust is very much blocked.Thanks for any help.

Not that I know of, and I don't recommend doing anything other than replacing it. You're free to try, though.

Almost anything you put on it will increase the mid range power significantly.

A two hp increase isn't much. Virtually any competition exhaust installed on the '08 will add 4 or more (some of them much more) at or around 5000 rpm. :thumbsup:

how many horses does the Dr.D add @ 5k RPM?

I've only ever seen one chart from an '08 with a DRD on it, but that one showed a gain of 6 at 4800, and a loss of 0.25 at peak. The caveat was that there was no effort made to optimize the bike with the stock exhaust. Then again, not much was done to the bike after the DRD was bolted on, either. Just some minor jetting.

I've only ever seen one chart from an '08 with a DRD on it, but that one showed a gain of 6 at 4800, and a loss of 0.25 at peak. The caveat was that there was no effort made to optimize the bike with the stock exhaust. Then again, not much was done to the bike after the DRD was bolted on, either. Just some minor jetting.

wow, 6hp is pretty significant. What optimizations or adjustments would you recommend to go along with the Dr.D?

is it just me, or did some posts disappear from this thread? including one with a dyno chart...

Yes I removed the last cone before it exits and cut the remaing non perfed part out flush, leaving the first cone in place. jetting is stock main and a 48 pilot with the fuel screw on 2.25 out. I have now sold my DR.D in favor of this set up. Good smooth power and still way quieter than my DR.D was at 99db, this one moded is at 97. I hope this helps.

Mine added 4-5 hp with the DR.D and a 13-75-1 piston.

I went to CA for a race and Air Fuel was 11.8 to 11.9 and i thig they shoot for 12.0, But that is real real close.

Guy that gave us a tour from Pro circut still beat me.

Made the bike harder to ride, but if you want power it works.

so you took the long cone out flush with the rear of the silencer?Thanks for your input!

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