I have a 1998 gs500. For the past few weeks it doesnt start with the starter like 60 percent fo the time, but always starts on a push start. When it does start on a electric start it takes a long time, there is a gas smell and then a huge backfire. After i have been riding for a while, stop quick and start again it does it with these huge backfires that sound like gunshots. Somes when it starts i feel this blast of air on the side of my left leg. about the knee level coming out of the bike. What is wrong with my bike?
Valve adjustment and left carb or carb boot not sealing/seated correctly.
Couldn't it also be a sticking or dirty float valve? If you remove the float bowl from the left carb, shoot some carb cleaner up in there and jiggle the float, that might clear it. Otherwise, remove the float valve and valve seat, check it for wear and clean it up.
Check to make sure you have good spark in both cylinders. If only one cylinder is firing the fuel from the bad cylinder will be pushed into the exhaust and may be ignited, causing your backfire.