Just bought a 2000 road king classic it has a popping sound when u let off gas and the bike is stock so I checked the plugs and the gap was less then .30 thread s was black and the end was white what is the gap on the plugs need to been and found a crack in one of the pipes it is a efi has 39000 on it and this is my first harley will the crack and plugs cause this
Thanks pat

 

the spark plug gap should be .038 to .042. and the crack in the pipe is causing cool fresh air being drawn in. leaning out the exhaust causing it to back fire on decel.

 

Crack in pipe is culprit . Even a loose clamp can do it. Fix the crack first.