Larry's right of course, but just because you have a backfire doesn't mean you are running rich. Does the backfire sound like popping or gunfire? Gunfire is an explosion in the cylinder with the exhaust valve open. Popping is excess gas burning in the exhaust.
First, I would pull all four plugs. If three of them show lean running and one shows black, that carb has a float or float valve problem. If the plugs indicate a fuel problem I would get a jet kit. I've read that GSX-R's run rich, but most older Kawi's have a lean stumble right off idle.
First, I would pull all four plugs. If three of them show lean running and one shows black, that carb has a float or float valve problem. If the plugs indicate a fuel problem I would get a jet kit. I've read that GSX-R's run rich, but most older Kawi's have a lean stumble right off idle.