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Your mostly right. The piston on its up stroke is hit by expanding air from the fuel igniting to soon. It hits the piston unevenly an before the rod is strait with the cylinder. Pistons fit in to the cylinder with a slight gap that gives them room to freely move up an down. The sudden, uneven hit causing the piston to cock sideways an the sound is the piston skirt hitting the cylinder wall an resonating threw the engine. The resonation is what gives it its nickname, valve chatter. The end effect is scoring of the cylinder walls, broken piston skirts or in bad cases the whole piston its self cracks. Its never good to hear a knock. Lots of bad things can happen.
Your mostly right. The piston on its up stroke is hit by expanding air from the fuel igniting to soon. It hits the piston unevenly an before the rod is strait with the cylinder. Pistons fit in to the cylinder with a slight gap that gives them room to freely move up an down. The sudden, uneven hit causing the piston to cock sideways an the sound is the piston skirt hitting the cylinder wall an resonating threw the engine. The resonation is what gives it its nickname, valve chatter. The end effect is scoring of the cylinder walls, broken piston skirts or in bad cases the whole piston its self cracks. Its never good to hear a knock. Lots of bad things can happen.