I have a 86 fxr was workin excellent.Now it keep losing fire on the rear cylinder and than kicks back in and so on.tried a few new pluga same thing.I havent changed or touched anything before this issue. Any help appreciated.

 

It could be a bad spark plug wire or a bad coil.

 

It could be a bad coil as previously stated or wires. I would also vedify that you have good compression in the cylinder as well. Lastly it could be a fuel problem. Check the carb and intake manifold for leaks.....

 

thanks i was figuring it was a coil problem.

 

No coil problem as I tried a brand new one and still same.I can't seem to detect any intake leaks.Found a exhaust leak on same cylinder.compression test between 120 and 125 psi per cylinder.beats me.Has a 2-1 header and is back firing often not constantly but often.