My Son has a 1983 XL600R that was in very rough condition when he got it. Some chuckle-head had wrenched on the inside without knowing what he was doing and the cam sprocket bolts came loose and chewed up everything. I've completely rebuilt the top end, including new cylinder, piston, rings, new head, valves and seats, etc. I've overhauled the carbs and installed a "Ricky" stator. The bike starts first-kick and runs great at low RPM. However, accelerating from 30mph and up just ain't happening due to what feels like ignition cut-out. I've convinced myself the carbs are adjusted properly. There are no air leaks causing lean condition. Coil checks out and of course the spark plug is new. Any ideas? Thank you!