Motorcycle Repair: 03 kfx 400, coolant tank, heat range

Question
QUESTION: Recently, as in yesterday, my kfx started shutting off after riding it for only a few minutes. I looked at my coolant tank and and radiator and I noticed that the radiator was clogged up with debris so I'm in the process of removing the radiator to clean it and/or replace it if necessary. My question is, should this fix the problem, or could it be something else that's more serious?
         Thanks,
         Daniel

ANSWER: Daniel, This will help in keeping it cool but it wont fix the problem. Its possible that the valves have seated into the head and you have lost the valve lash clearance. I am familiar with this problem as my son races a kfx and the valve seats will pound up into the head and the shims need to be resized to get the valve clearace back. Its even worse if you are running a Web cam and valve springs or the Hot cam and springs. These are a little stronger to close the valve faster and work them a lottle harder. Get the valves set and try again and see if this helps.

---------- FOLLOW-UP ----------

QUESTION: I just had the valves shimmed last week, so would that make a difference in whether or not the valve lash clearance is the problem? Or does that not make a difference at all regarding the valves?

Answer
Daniel, This should help the valve lash situation. Hopefully the overheating problem with the radiator plugged did'nt damaged the motor or headgasket. Make sure the carb is clean and adjusted properly and that the fuel from the tank does'nt get restricted. Also check the spark plug to see what it looks like. If its dark it may be to rich or the plug is the wrong heat range. If its white it may be lean or running to hot on the plug.