I can sure make mine do this through jetting! You still use the fuel screw to get the pilot, but the leak jet, just have to change it, or get an adjustable set up. I cheat, and use the choke to see if it makes the fire and popping better or worse. BUT, what Joe said, will do this also, bad seats. How do you know, how many shim sizes the bike was from new? 3 strikes, they are toast. Take the head off and pour fuel in for leakage works also. My exhaust valves are beating my intakes. Pete and Eric are around.