Hello,
My snow thrower started making a knock sound under hard load recently...it is only 2 years old very little use....I think perhaps the head bolts are loose.....no visible exhaust leaks ...and every time I heard the knock I shut it down ...any thoughts and anyone know the torque specs for head bolts? Thanks :)

Hi,
Doubtful that it is head bolts. "Under heavy load" seems to indicate it is something to do externally to the engine, assuming that the oil level is correct.
Peace,
Clarke