2000 carbureted Fatboy is giving me some backfire noise on deceleration, particularly if I am going downhill and engine breaking. First time in 20 years I have had this issue. Took it into the shop and they replaced the exhaust and intake gaskets but no improvement.

Any advice would be appreciated. Thanks

 

Decel pops are frequently associated with exhaust leaks. Did your shop carefully inspect the pipes for cracks? Even a very small one can cause this.

 

Exhaust baffles need to be repacked , perhaps your carb has gummed up and need a good cleaning , try running a couple tanks of sea foam through it , 1 once per gal .

How's the air cleaner ? A plugged / dirty air cleaner can cause a rich condition causing backfire . Intake leaks perhaps , bike at idle , spray some TB cleaner on them and see if the idle changes .

Clean the carbon out of the TB , tooth brush and some TB cleaner or sea foam will do , do the butterfly and seat as well .

Does your bike have stage 1 or just stock ?

How does it run / idle otherwise ?

 

Try increasing the idle fuel a little. If there's a lean condition on decel you'll get popping. A leaky head pipe will also cause popping.

 

Exhaust leak or lean condition is a common cause of a deceleration popping

WP

 

Great feedback guys - thank you

 

popping is caused by accumulation of unburned fuel in the exhaust. normally with a correct working carb, the fuel is too lean to burn on a decel and exits the exhaust with no issue. in this situation, extra air from leaks does nothing. but for grins and giggles, we add in extra fuel, still to lean to burn in the chamber, it will accumulate in the exhaust till it reaches a point where it can ignite and cause the pop. so have you reset the idle mix? is the throttle stop too far open? have you checked float height?

 

Do you know what brand carb you have, and the number of the pilot/slow jet? Perhaps you might check if the pilot/slow jet needs to be increased to the next higher number to eliminate the lean condition.

 

If it did not do it before and is doing it now . Question is what changed. Check and check again for exhaust leaks. It often does not take much.