Man enough.... LOL... I'm going riding in about an hr.... More than you can say.

 

If the plug was a 1/4" to long. Theres a good chance it would hit the top of the piston. I doubt the plug is the problem. The plug will not make the quad run hot. To lean of a fuel mixture will make it run hot, surge and be hard to start. Have you removed the plug and examined it. You should be able to tell how the motor is running. You may want to remove and clean the carb. While you have it open. Make note of the numbers on the main jet, pilot jet. If the needle is adjustable make note of which notch the clip holding it is in. This will give you a baseline on how the carb is setup if changes are needed. A air leak around the carb could also make the quad hard to start and make it run lean and hot.