I get a few backfiring pops from the muffler after hard acceleration and immediate release of the throttle.

I tried a run without the air cover and still backfiring and it ran a little worse.

Any ideas?

 

Howdy,
the description that you give would usually mean that you have a lean condition. Try opening up your idle mixture screws about 1/4 turn & try again. If that doesnt help you may need to jet your idle jet up a size. Have a goodun!!!

 

Additional Info:

I've got 124 front 128 rear mains.

I'm sitting at about 3500 ft.

I just pulled the front spark plug and it was filthy black.

 

have you upgraded your choke springs... they may be hanging up ???

 

I have had this problem in the past. You are running a little lean for sure. Do as Ross650 said and open up the mixture screws 1/4 turn to start with. That will fix your problem.

 

My V backfired like that until I found and fixed an exhaust leak. My pipe was not tight enough on the motor, and it sucked air and backfired every time I let off the throttle fast. Just a thought.

 

That's what the troubleshooting guide with the DynoJet kit says.

"Main jet, needle, and slide have no effect on deceleration."

"If you have popping on deceleration make sure you have no air leaks in your exhaust pipe, intake manifolds, vacuum lines, etc. If there are no leaks try turning your mixture screw out 1/2 turn."

I hade the pipe off in order to cut the end off I'll have to double check those fittings. Anyone have a torque setting on those bolts?


I still am thrown off by the black spark plugs though.

 

Try holding your hand over the exhaust for a second, and just listen for the leak. I had no problem hearing it on the V.

 

My 02 Prairie used to tell me that it was time to clean it's air filter by backfiring out the exhaust. More of a "pop", after acceleration and throttle shutdown.