Backfire type "bang" happens from time to time

Hi all!

Last weekend I replaced the header pipe and I've noticed more top end,

it goes very well but from time to time, when I turn off the throttle (specially

when pushing the clutch) it makes a loud backfire (only one).

I've checked if there is any leak in the exhaust, and I think there isn't anyone.

What do you think is the cause? Perhaps a small pilot jet (the stock one)?


I remember burned mentioning that it would be normal to get a small backfire or popping sound when transitioning from on throttle to off throttle if your jetting was just a bit rich (too much fuel) but just about right-sort of on the safe side of perfect. Is that the sound? If so your can fine tune it by adjusting the fuel/air screw on mikuni carbs, dont know about fcr carbs.

What do you think I should do? Leaning the air/fuel screw or richen it?


Be very sure there is no leak in the exhaust. We had the same issues with my sons KLX300 after he put on a bigger header. After much playing with jetting :banghead: we pulled the exhaust back off. On close examination we found some slight black soot on both joints. It wasn't much but when we sealed it up properly the problem went away and we could jet the bike to run properly and consistantly. :banghead:

What do you think I should do? Leaning the air/fuel screw or richen it?

lean it (screw in 1/4 turn at a time until it runs better. If it doesnt run better, ?????? :banghead:

Sounds like it running great to me.

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