How do you time a 1988 sporster it keeps popping through the carb i have advanced the timing and changed the plugs but still does it?

Answer 1

really need more info on the bike's performance to rule out certain items, but here goes. i am going to assume electronic ignition and hydraulic lifters. remove timing cover to expose pickup plate, remove timing plug on engine crankcase and use a clear timing plug (available from hd) in the hole. you might want to roll the engine over and clean the advance mark of oil and paint it so it will be easier to see through the plug. crank the engine and at high idle (2000 rpm) and turn pickup plate to align timing mark in the middle of the hole with a timing light on front cylinder. if you got a voes, you need to remove hose and plug it first. you said you advanced the timing already but if it is too far, starting would be a problem on the starter. you could have a lean condition in the carb also that could cause cough back. like i said, need more info. however, i will throw this out to you. if the bike is a high miler, check the rocker arms. why, you ask? i have a 1974 xlch with well over 100k and it developed a problem of free wheeling on starting. the rocker arm had worn down and left a little ridge on the end which at times caused the engine to seem like it was free wheeling but really was rolling up on compression on one cylinder which would cause it to roll backwards being the other cylinder had a stuck valve (valve tip hanging rocker). all you have to do is re-arch the rocker pad to make it smooth again. also a bad plug wire can cause this, i run solid wire core on mine, no electronics.