Remove the fuel inlet nipple from the carb. Check the hole where
the fuel passes into the needle assembly and see if your's is
mis-alighned like mine was. Also check to make sure the nipple on the
muffler that pressurizes the fuel tank is drilled correctly, and also look
at the nipple you removed on the carb inlet for a nice clean inlet hole.

You are not getting enough fuel into the carb, and it is leaning out. This
is not good, because it causes overheating, and could damage the engine. []

It is easy to fix.