My Harley Davidson heritage softail has an annoying backfire from the rear cylinder when I let off the throttle on the freeway or when I'm coming to a light. I just had the top end rebuilt completely rings valves heads refaced etc plugs are new exhaust system is tight no leaks. Now the bike is only 4 years old but I do have 99k on the motor.. Any ideas??

 

Wow, a Vietnam Harley. Welcome to the forum!
Maybe a mod can move your post to the appropriate discussion room, "off topic" is not correct.

 

Possible intake manifold leak.

 

Would be the first place I would look.

Mine was doing the same.

Applied some thread locker and torqued to spec. and all is well.

 

You better take it to an authorized Harley Davidson Dealer.

 

After all that work....give it to a tuner and tune it out and maximize all the work you had done. I had annoying decel pop after 106 job was done. I pin pointed what Rpm's on decel and what speeds it happened at, told my builder/tuner....he dialed it out.

Once in a while I get a pop or two but not like the machine gun popping I had after the build.

 

Unburned fuel. Probably running too rich.

 

Common problem when changing exhaust/intake/etc. Air/fuel ratio needs to be adjusted, which can be done in a number of ways (dyno and tune, flash tuner, etc.)

 

Take it to a reputable tuner.