Spark plug electrode damaged top of piston

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OK, so lets take this step by step. I'm not convinced the plug electrode "fell out" and destroyed the piston crown. That surface of the piston crown had debris bouncing around for a while while the engine still ran before the engine quit. If the plug electrode fell off and was banging the damage would have been very minimal as the engine would have died instantly from lack of spark. I think what did happen is something large enough to create gouges in the piston crown got sucked past the air filter and into the cylinder (like a small metal screw /washer , small rock pebble )and that piece actually broke the plug electrode. You might find some debris down inside the crankcase. Did you do any recent engine work with the air filter removed ? I'm really surprised the cylinder ports are not all gouged up. By the looks of the indents on the top of the piston looks like some type of round piece of debris.
 
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Polar_Bus said:
OK, so lets take this step by step. I'm not convinced the plug electrode "fell out" and destroyed the piston crown. That surface of the piston crown had debris bouncing around for a while while the engine still ran before the engine quit. If the plug electrode fell off and was banging the damage would have been very minimal as the engine would have died instantly from lack of spark. I think what did happen is something large enough to create gouges in the piston crown got sucked past the air filter and into the cylinder (like a small metal screw /washer , small rock pebble )and that piece actually broke the plug electrode. You might find some debris down inside the crankcase. Did you do any recent engine work with the air filter removed ? I'm really surprised the cylinder ports are not all gouged up. By the looks of the indents on the top of the piston looks like some type of round piece of debris.
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I tested the spark plug and still had a spark without the tip of the electrode, I looked down In the crankcase area there is nothing down there. I never removed anything on the engine to let anything in, that includes air filter or exhaust. So not sure what else could be in there.
 
Manny said:
I tested the spark plug and still had a spark without the tip of the electrode, I looked down In the crankcase area there is nothing down there. I never removed anything on the engine to let anything in, that includes air filter or exhaust. So not sure what else could be in there.
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Wow, that is crazy, ive heard of electrodes falling out but never heard of only a piece of the electrode breaking off and still allow spark. With that said, now i agree and the damage outcome makes sense.
 
Polar_Bus said:
Wow, that is crazy, ive heard of electrodes falling out but never heard of only a piece of the electrode breaking off and still allow spark. With that said, now i agree and the damage outcome makes sense.
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From what I can see the tip of the electrode is very hard piece of metal and the rest is copper so if that tip breaks off there is nothing preventing the spark from still being transmitted to the ground electrode. 50309
 
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