I'm in the final stages of getting my 87 600 project bike on the road. The bike starts fine and with a normal amount of choke. The carbs have been rebuilt, float heights are set, all o-rings on the carbs replaced with OEM parts. It runs pretty well; with the exception of the 5.5K rpm range but I'm currently dialing in the jetting due to the full Delkevic exhaust (no baffle). I've noticed that often, when I hit a hard bump, the bike will act like it's dropped a cylinder and idle very poorly. Then, fuel will come out of the overflow for carbs 3/4. Sometimes it will recover, others it will stall. I can restart it with the choke and some heavy throttle; then it will clear up. I've tried wiggling wires, including the plug wires, bouncing on the bike while it's parked, and I can't seem to reproduce this while sitting still.

Any thoughts?

 

sounds like a sticking float valve or one of your floats is taking on fuel re-check float heights etc.