Back firing from number 4

Can anyone give me some reasons for backfiring through my number 4 carb...thanks...Its a 1982 kz750 spectre

it has a 4 to 1 exhaust also

hotdogg wrote: Can anyone give me some reasons for backfiring through my number 4 carb...thanks...Its a 1982 kz750 spectre

Possibly insufficient clearance on the intake valve.

Good Fortune!

thanks bud

Is it backfiring throughout the rpm range on only at idle? If it is at idle or very low rpm it may be the carb holders. You can easily check them to see if they are leaking; if they are the bike will very likely backfire at low or idle rpm (mine did). Here's some info on the carb holder test. Ed

www.kzrider.com/forum/3-carburetor/59338...sync-78-kz750#628442

it does it when i rev it and on the way back down to idle..but not at idle..

If not already done, would assure functioning of the timing advancer by viewing it with strobe-type timing light, and watching for the arms to quickly move back and forth as rpm is varied by blipping the throttle.

It's possible that the advancer is hanging slightly and not immediately returning to fully closed idle position when the throttle is closed.
Perhaps the pivot points need lubing (sometimes possible by accessing through the timing window).





The advancer should NOT look like this:





Good Fortune!

I will check that tomorrow. Thanks a lot you have been really helpfull

It was the advacer was stuck but I replaced the card boots anyway.. Thanks a lot I would have never found that timing problem..