Two things come two mind if it blows while mowing. First, I would check for frayed wires. Might find one that is shorting to ground as you are bumping around. Start a the clutch and work backwards. Tough to find with a meter, as it may not be touching, need to use your hands and eyes. Second, your clutch may be overheating, causing a short when it gets hot. Next time it happens, check the clutch with your hand. It should be warm, but not hot.
