Motorcycle Repair: question on 4 wheeler, pilot jet, fuel mixture

Question
my son has a 2000 honda 400ex, it runs great but the exhaust overheats after running only a few minutes. Everything seems to check out fine with the engine any suggestions as to what the problem could be? Thanks

Answer
Debi,

some bikes do run quite hot these days
but check the spark plug color and
if it is very light colored it may be a
plugged pilot or idle jet in the carb.

-If the air cleaner or exhaust pipe
has been modified it may need rejetting
of the carb to a 155 or 158 main jet and should
have a #40 idle pilot jet.

-The clip on the carb slide needle can be
lowered one notch, this will richen the
fuel mixture to cool the engine.

-If the spark plug is very black or sooty,
it may have a plugged air filter or pipe.