I'm having an issue with my 84 Yamaha stalling after running for a period of time (say about 5 minutes or so). I bought it well used, so I've cleaned and rebuilt the carb, cleaned the gas (and oil) tank, new fuel and oil lines, new spark plug, new throttle and choke cable. It starts on the first kick and idles well, but if I rev the motor and let off repeatedly (I'm trying to duplicate a driving experience, as the wheels and brakes have yet to be addressed and the bike cannot be ridden), it will rev to an extremely high point, bog out and not restart. Once it cools overnight, it starts up perfectly. Any thoughts as to why it might be cutting off?