What causes the machine to run hotter when the air filter is clogged? And can this cause overheating?

 

A clogged up air filter will cut down on the amount of air, and that should make your mixture rich, not lean. Usually, one associates running hot with a lean condition, so that doesn't fit a pattern. Might be some other problem????

 

Ditto here!! Dirty air filter richens you up, and therefore shouldn't heat it up.

 

Water cooled??? If so, maybe you have a cooling system problem???