what causes backfire at idle?

[quikvrsixx]

the bike has no mufflers and pod filters. just had the carbs completely redone and a dj state 3 kit installed. bike runs good but at idle it will backfire and sound like its going to stall but doesn't. i adjusted the idle up a little but the backfire still occurs.

 

[drtybykr]

i would guess lack of back pressure

 

[Guest]

Is it backfiring through the carbs or the exhaust?

 

[Qdude]

Through the carbs?
Oddly enough, often backfiring can be caused by over lean settings.
No mufflers? Pod filters? Both allow air to move more easily through the system, "lack of backpressure" as drtybykr posted. This allows more air per unit of gas causing lean conditions.
Be sure to check the possibility of air leaks on the intake manifolds.

 

[tkent02]

Mine does it when the choke is on too much, so too rich can do it too.

 

[quikvrsixx]

thanks. it has seemed to mellow out now that the bike has ran a few times down the road. one problem i did find is that i forget to reinstall the exhaust clamps on the h pipe under the bike, so i am not sure if that had anything to do with it. still needs some adjusting though.