Motorcycle Repair: backfiring, gas fumes, gear shift

Question
i just changed the gear shift seal on my 98 1500 vulcan classic and after i put it together it started back firing. i changed the spark plugs and still no change.

Answer
Tony,Check the pipe to cylinder head nuts they may be loose also some of the 1500's had a resonator chamber under the frame for the exhaust to give it a better sound. Check all the clamps as the exhaust might be sucking air allowing it to backfire by burning the raw gas fumes and new air in the hot pipe. Some of the earlier 1500's 96-97 had a update installed on the carb. We had to install a small heat tube on the bottom of the carb to warm it to stop some of the backfiring,this was Kawasaki,s quick fix and the later on thay came out of the factory with them on the bike.Some were heated with water and some were heated with an electric terminal threaded into the carb,make sure the wire did'nt fall off.