Small Engines (Lawn Mowers, etc.): low oil, now loud, broadmore, crankshaft

Question
I have a simplicity broadmore with a 16hp motor.  I was cutting my lawn yesterday and noticed it got pretty loud and was viberating.  I checked the oil and it was very low(I had to put about a quart in).  what damage have I done? I'm sure I cooked a seal, but I do not see any oil leaking any place. Please help.

Answer
If the oil was very low, it's possible the engine is on it's way out the door. If your are hearing loud knocking sounds, The rod has probably started to overheat and caused the bolts to loosen and it's slapping around on the crankshaft. If this is so, it may be time to look for a new engine. There probably won't be anything leaking now, but if you run it too long, it will break and put a hole through the block.