Tearing down a 6 HP B&S off of a Crapsman push mower for a friend tonight. Compression was around 40 PSI and the thing wouldn't start even with ether. I figured a stuck valve or broken spring. Got that far and they were OK. Got ready to split the crankcase open and turned it up on it's side to drain the oil and something rattled inside. As I drained the oil a 1" long bolt fell out of the oil fill hole!! Went ahead and split the case and two teeth were sheared off of the (plastic) timing gear that is connected to the (plastic!!) valve cams. Problem found. I think that damn bolt was in there when they built the engine and it finally worked it's way into the valve cam gear. It was in the wrong place at the wrong time. I also noted there are no lower end bearings in this B&S. Just the aluminum case journal type "bearing" that the drive shaft goes through. Wow! I don't know how these things hold together. I hope I can at least buy the replacement gear/camshaft assembly in metal, but I doubt it. No question for anybody here...just postin' for general knowledge of what's inside a B&S IF you elect to purchase one.