06 wr450 backfire problems

I recently bought an 06 wr450f and it has a hmf slip on exhaust installed. The bike backfires sometimes. Is this a big issue? I'm buying a quiet core and spark arrestor insert for the muffler. What exactly should I be rejetting on the carb, if anything at all? Thanks

You need to give us a little more information then that like...elevation. Be a good idea to go through the entire carb to see what you got in there. Backfire is your lean on the fuel screw. You might need to open it up a 1/4 or 1/2 turn. You also could be lean everywhere else like pilot jet.

1300 feet, could the backfire damage my engine though?

You have a lean condition caused by an air leak.


No reason to change jetting if it ran well before with the jetting you have, unless you went up 8,000 ft......



Fuel screw

Muffler joints

Air boots




..corroded and leaking hot start plunger <<<<< very common

Edited by KRANNIE

Also check to make sure the little rubber boot on hot start nut is properly seated.

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