Motorcycle Repair: 86 fxr backfiring out exhaust, plug wires, good luck

Question
QUESTION: hi Mike, i have 1986 fxr. new plugs,new plug wires and new coil.the carb was rebuilt a month ago. the bike starts fine and idles great when i pull the throttle back about a 1/4 it starts to spit and sputter and backfires out of the exhaust not the carb. please help.

ANSWER: Pull the plugs and let me know what color they are. What carb are you running?
Mike

---------- FOLLOW-UP ----------

QUESTION: It's a Keihin carb. The plugs are starting to turn black. Thanks for getting back so fast.

Answer
The black plugs means your bike is running rich or not a hot enough spark. Since you changed coil and plug wires it would make me think you have a carb problem. I would have the carb checked to make sure it was rebuilt correctly.
Good luck and happy riding
Mike