My 1992 John Deere has started making a knocking noise when running. Does it moving or not. BUT when you push in the brake and clutch it stops making the racket. I've checked the oil, its fine, motor sounds fine. Checked the pullies, they are all tight and fine. Start the blades it mowes fine, not a bent blade and all those pullies move freely. Start moving it mowes fine and pulls fine, just makes this very annoying knocking sound. When you push the brake and clutch in to stop, it stops let off, it starts again. Any ideas?

Hi,
Check the engine mount bolts. Bet they are loose and/or some missing. Should be four.
Peace,
Clarke