Screamin Eagle II

I've got HD Screamin Eagle II (Baloney Cut) slip-ons on my 03 FXDWG. Also had them on my 01 FXDXT. On both bikes I also had a dynojet carb kit and KN Filter combo. My problem is the slip-ons continuously explode (backfire?) out the back whenever I have excellerated hard and then roll-off the exhaust also if cruising steady and down-shift through the gears. Sometimes it's "Cool" but for the most part it's becomming annoying. The HD dealer says it's due to vaccum inside the pipe which sucks in cooler air causing the explosion. Other HD slip-ons with a different cut don't do this. Dealer says live with it. Any suggestions out there?

Hi, I don't buy what the dealer is telling that your problem is because of the baloney cut I have slash downs which is the same thing rotated 90 deg down and don't get loud backfires on decell however sucking air into the exhaust can cause the problem make sure all your clamps and gaskets etc are tight and not leaking air leaks are one of several causes of your problem check out the American Mikuni website it lists all the causes etc in their troubleshooting guide its an excellent resource good luck Rob

Exhaust Popping

From your explaination it seems that you are expeiencing "lean misfire". This is caused by cutting your throttle which closes off the carb, the engine is still spinning fast as it declerates which causes it to still pull in fuel/air through the carb. The mixture is not rich enough to ignite in the cylinder so the unburned charge is dumped into the exhaust. When this charge has sufficient volume to to get lit by the hot pipe you have a good bang! You should check your low speed jet and also the mixture screw to remedy this. Also check for any air leaks in the exhaust system, especially at the head and also the joint between the pipe and the muffler.

Thanks VYBR8R.

I've currently got a 190 main jet and have the mixture set around 3.5 turns from bottom out. I'll try the mixture increase and progress toward a increased slow jet. I have serviced the exhaust today i.e. Silicone Hi-temp gasket around the muffler/header connection as well as the crossover pipe. The head pipes are tight with no sign of exhaust leakage.
It's getting cold up here so times limited (Ottawa, Ontario, Canada) but I'll proceed and let you know how things go.

Additional thanks to allanr5. American Mikuni site wasalso a good find.

Thanks again.

Roadrunner

Thanks Vybr8tr, followed your advice. Changed exgaskets and sealed all other joints with hi-temp gasket. Bangs and pops 80 percent cured. Only the tail opening vaccum pops left. Great!