Have you checked your fan and/or water pump? How about the radiator, is it clogged with debris, air needs to be able to flow through to carry out excess heat. Also, check the spark plug, you may be running a bit lean, this can cause the motor to run hot. This could be caused by debris in the carb, you may need to take the carb off, disassemble and clean it really good. Good luck.
Yours truly, sincerelly, love always, Josh aka The DirtDemon.