My son recently purchased an 82 Nighthawk 650. The bike is in great shape, and the previous owner had the carbs completely re-built, and the fuel shut off valve replaced. The bike runs great, but sometimes it when it is hot, during stop and go traffic, it will just quit. It is getting gas, and if he lets it cool for a bit it fires up fine with no problems. Any suggestions on where to start checking? Battery is new, and there is always plenty of juice to crank.