Motorcycle Repair: BACKFIRING, suzuki savage, diaphram

Question
I HAVE A 1987 SUZUKI LS650 SAVAGE AND IT BACKFIRES MAINLY WHEN THE BIKE IS SHUT OFF.SOMETIMES THE BACKFIRE IS JUST A SMALL POPPING SOUND AND OTHER TIMES IT IS LIKE SHOTGUN GOING OFF.I HAVE TRIED DIFFERENT OCTANES OF GAS,BUT IT DIDN'T SEEM TO HELP MUCH.PLEASE RESPOND.THANKYOU FOR YOUR TIME.

Answer
Hi Jeff...

Man, I love the Suzuki Savage!! They are a fun bike to ride, and cuz they are a single cylinder with one carb, they are also usually easy to fix. Has the bike always done this or is this a new problem that started without warning? I ask because there are a couple different things that can cause this to happen. Have you altered the exhaust system? Let's assume that the bike used to run fine and this just started happening out of the blue. There are two areas that can cause this problem... ignition malfunction or carb problem. The ignition is easy to check. There are two ways to properly shut off the motor. The engine kill switch on the rightside handlebar switch, and the ignition key switch on the left lower side of the bike. If the bike backfires when both of these shut off methods are used (independantly)then the problem is in the carb. If the backfire occurs only when one of those switches is used, then there is a bad connection in the switch that is causing an extra spark to occur at the moment of shutdown. (God, I hope that made sense!!)Now, if it backfires no matter which switch is used to shut it down, then you have a carb problem. Specifically, the float level is too high or the air cutoff valve is faulty. The air cut off valve is behind a cover on the right side of the carb. It has three screws holding the cover on. Behind that cover is a spring that pushes on a small diaphram. It is vacuum operated. If that diaphram has a tear or small hole in it, it can cause backfiring. Try the things I mentioned and let me know if ya need more help! Good luck Jeff!!

Jack