seetz,
I'm with you. I would install new plugs and change the oil and see what happens. The plugs could be so fouled and coked from the high temps that they are not firing properly or completely. This might show as incomplete combustion in the form of black smoke.
Sticking new plugs in is pretty inexpensive and might just get you out of the woods...try it first.
As Tiny mentioned, be sure to at least look at the carburetor and any hose or wire that might have suffered with the high temperatures. That's my two cents worth.
Stuart
