exhaust backfire

ok, i cleaned the carbs and put her back together, except now im getting an occasional backfire through the mufflers on deceleration. any clues?
thanks
Dave

 

Correct me if I'm wrong, but an exhaust backfire usually indicates a rich mixture, unburnt fuel is making it into the exhaust and igniting in the pipe. Thats the cause, and some one much smarter than me will come and give you the remedy to your problem.

 

Most often, as I have experienced, backfire upon deceleration can possibly be traced to extra oxygen in the exhaust helping to ingnite unspent fuel.
Maybe a leaking header pipe gasket or exhaust flange clamp.
On Maxims, I have seen small holes rusted through in their 4-into-2 collector boxes which allow air into the exhaust.
My Venture used to backfire until I clamped off the AIS system.

Good luck.

 

I thought this was due to being too lean?

 

If you are backfiring through the exhaust ... It's time to check your Valve Clearances.

A tight Exhaust Valve will backfire the exhaust. It tips you off in time to do the adjustment ... usually ... so, don't let it slide. Get that cover off there and measure your clearances!

If you have a tight one ... adjust it ... or, you'll Burn it and wind-up pulling more than the Cam Cover. You'll be pulling the Cylinder Head and doing something about a burned valve.

 

Since you stated that the backfiring started after you cleaned the carbs I'm leaning towards Ace_Frehley's diagnosis. However, RickCoMatic's advice should be heeded because the problem may have been there the whole time but was being masked by poorly adjusted carbs. I would check/adjust the valves then do the same to the carbs with carb sticks followed by your colortune plug. Finally MidniteMax is right about sucking air. You should give your exhaust system a once-over to make sure it's in good shape. I guess what I'm recommending is: do all three. They're all excellent suggestions!