Small Engines (Lawn Mowers, etc.): knocking, piston skirts, endcap

Question
i have a 17hp B&S model# 311707 type-0132e1 that is knocking. i assumed it was a bad rod so i opened up the engine. connecting rod looked good no play on crankshaft or on wrist pin i did notice some scoring on piston skirts and cylinder wall but did not seem excessive. i also noticed there was a lot of play in the counter weight bushings so thinking that the counter weight was causing the knocking i installed a new one. i put the engine back on started it up and still knocking like crazy, so now the only thing i can think of is piston slap. the cylinder walls look good still have crosshatch pattern do you think i should replace the piston or is there something else that could be causing the knocking?

Answer
john
Your engine is about to blow. That knocking sound is indicative of a connecting rod bearing out of tolerance. This condition never gets better; it'll finish out by breaking the endcap on the rod, and usually puts a hole in the block. Sometimes, it can be caused by a bolt coming loose from the endcap, and I've had success by taking it apart and tightening the bolt, fixing the problem for at least several years. This can only be done if there isn't any deformation from it knocking