Rejetting for exhaust insert

Are there any general rules of thumb for jetting when putting in a more restrictive tail pipe insert?

I have an 01 426 Supermoto with a Yoshimura RS-3 full pipe that I race without any inserts and the bike runs great. For an upcoming race the sound level is 96 decibels, which should be achievable with the medium Yoshi insert. I have tried the insert with the current carb setup and the bike runs very badly, what do I need to adjust/change?

Drop the main jet 1 size and see if you can re-tune the pilot circuit with the screw. If not, drop the pilot also.

I ended up dropping the main from a 175 to a 172,

dropped the pilot jet from a 48 to a 40, and raised the needle one clip. The power delivery is smooth, no popping on deceleration, sweet :D

With a 40 Pilot, you may be WAY too lean unless you're in the 10,000' range and then it still might be a stretch. I'm at 5000' and I'm running a 45 with the JD Red #5. I'd be willing to bet that the 172 Main is compensating for the Pilot circuit with a bit of overlap. You may be running well, but it sounds off and is likely having some effect on your valves and such that you can't detect...SC

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now