what would cause this?

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Wrist pin was pitted directly under the bearing....

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another shot

[Logan #34's Dad]

Heat for one. Little lean maybe or oil to gas ratio is too low.
I'd say your not getting enough oil mix. Thats what lubes everything up.

[Coley'sdad#8]

lean which creates heat. is this a stock setup? how much time is on it? and what ratio ya mixing?

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I run 32:1 using an oil mixing cup for measurement. I did run the oil mixer for a while when I bought it brand new, but changed it a couple months ago.

I normally run 93 octaine gas, it's still stock. I watch the plug and it stays brown. The piston looks good, rod and the rest of the cylinder also look ok.

A friend said it may be pinging and rattling the piston a little. The cylinder wall looks good.

I am putting it back together with a new wrist pin, everything else stock, guess I will just have to watch it. Just wondering what I was doing wrong to cause this.

[Coley'sdad#8]

definately put a new pin bearing in it also. order one that is better than stock because if you put that motor back together with the original bearing your motor will be a yardsale shortly.

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got it, thanks.

[Coley'sdad#8]

1lap you have pm