After doing some further investigation,I narrowed the problem down to electrical. I am going to replace the ignition switch and the voltage sensor for starters. The battery shows a good charge and always did. I ruled out the stator and the rectifier as being defective since the battery maintains a charge. The coil still could be the problem if the engine dies out after getting hot.I will replace the coil if the new ignition switch and voltage sensor don't solve the problem. I also checked the plug wires and replaced the spark plugs,both are good and seem to get good spark. All neutral safety switches are good and I could not detect any shorts in the wiring harness. I plan to clean all the electrical connections and then give it a try. Thanks for everybody's advice from my previous post. I'll let you know how things progress.