YZ450F Backfire

[acetherizzle]

I just bought a used 2003 yz450f. it runs great and handles real well, but after I release the throttle the bike tends to backfire quite a bit. I tried cleaning the air filter, i changed the oil, put in higher octaned gas, and rode it to clean it out but it just keeps backfiring. I heard that some backfiring is normal though. does anyone have suggestions?

 

[Rich Rohrich]

The first thing to do is make sure you don't have any leaks in the exhaust system at the head pipe or the muffler joint that could be pulling in cool air and contributing to the back firing. Second thing is you want to make sure the air jet passages in the back of the carb are clean and the pilot jet isn't partially blocked. Assuming all those things check out you can richen up the pilot circuit to minimize the backfiring , but keep in mind that these bikes run best when a small amount of backfiring is present.

 

[Ol'89r]

They do tend to backfire on decelleration.

If the backfire is excessive, check the exhaust system for air leaks. Make sure the copper o-ring at the head is good and also check where the silencer connects to the head pipe for leaks

Also, check your valve clearance.

 

[Ol'89r]

Oops, sorry Rich.

Looks like we posted at the same time.

 

[Rich Rohrich]

LOL, great minds thinking alike Terry :)

 

[SFO]

You might try tweaking your fuel screw richer but it could kill your throttle response.

 

[Cheater]

Mine was backfiring alot, changed the jet and the problem was gone.

 

[Daddio]

Backfire is an indication of lean mixture. Not enough gas...