426-Yoshi Pipe -Quiet Insert Trouble


4 replies to this topic
  • BergRyder

Posted August 27, 2005 - 09:08 PM

#1

I have a 01 426 Supermoto with a full titanium Yoshimura pipe. For supermoto racing I have the pipe wide open and the bike runs great. For an upcoming race there is a 96dBA limit for the class I want to run in. I tried the two quiet inserts that I have for the pipe and the bike ran really badly. With the most restrictive insert I could only turn the throttle about 1/4 turn then the bike would miss, it was slightly better with the less restrictive insert but still ran badly - unrideable let alone raceable. Any ideas for how I can fix this? This method of making the bike quieter by making the exhaust opening smaller seems to rob a ton of power. There is nothing that can be done with exhaust packing?
Does the stock muffler fit the Yoshi head pipe (doubtful).
I don't want to do any thing too radical to the bike as this is a "one off" race and the bike runs great with the current set up.

  • BergRyder

Posted August 28, 2005 - 07:57 PM

#2

Update: I've been given a complete stock exhaust from an (03) YZF450, I've put it on and the bike is much quieter and it seems way less restrictive than the Yosh pipe with the inserts. Not sure how it will be on the track with the jetting I have.
Does anyone know the decibel level for a stock 03 YZF 450? From other posts that I've read seems like it's way over 96 dBA...

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  • BergRyder

Posted August 28, 2005 - 09:13 PM

#3

The following thread connects to a large list of different Yamaha model's and shows their decibel levels with different aftermarket exhaust systems.
http://www.4strokes....maha/yamaha.pdf
From the list it appears a stock 2003 YZF450 makes 98.9 dBA.

  • Scotty426

Posted August 29, 2005 - 05:25 PM

#4

I run the DR. D 3 and 1/2 pipe and had something similar. It ran great before the quiet core insert but had a bad stumble low in the RPM range with the quiet core. I jetted most of it out. It was the opposite end of the RPM range as you though. Just a guess on the face of it, you are rich on the main. The insert bleeds off a little air in the mid-high range and you get a rich sputter. Your call, but I would try going one leaner on the main. I have heard people same older Yammers run best with loud pipes but have never had anyone explain why. Curious.

  • ONLY4STROKES

Posted August 29, 2005 - 08:00 PM

#5

Update: I've been given a complete stock exhaust from an (03) YZF450, I've put it on and the bike is much quieter and it seems way less restrictive than the Yosh pipe with the inserts. Not sure how it will be on the track with the jetting I have.
Does anyone know the decibel level for a stock 03 YZF 450? From other posts that I've read seems like it's way over 96 dBA...


99db...and thats according to the man himself, Doug Dubach.





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