We have and XR600R that will run somewhat. The motor was just completly rebuilt and it will start after lots of kicking. There is fuel on the plug after kicking so we ruled that out, the engine has compression and air so we checked the spark. It is a yellow spark. no blue. so we put a new ingnition coil in it and it didn't seem to help the problem. Any other ideas? Loose conection, stator...???