I was in the process of rejetting my cousin's first motorcycle (gs500e no less ), I used the jetting matrix and put just one washer under the needle. it stared up good and sounded good at idle, but that's it......When it gets up to about 4-7k rpm it stunbles, backfires and almost died if I hadn't let off the throttle. I let it cool off and checked the plugs, they are slighly grey, so I'm a bit lean, but I think it is lean in the mid range which would be why it stunbles and backfires when the throttle is 1/8-1/2 way open, then at WOT it just shuts down like it's over flooded with fuel? I didn't read Kerry's float idea....i took the carbs back off and measured the float height. There with-in spec to the hanyes manual....Will another washer get rid of the leaness and get rid of the backfire? If not then I guess its an electrical spark/ timing issue....

What are some common signs of leaness? Other than the throttle hangs after a blip, and rich would be it dives below idle after a blip...