Why did I spin a main bearing?

zinser72 said

not sure. i havent taken it apart yet. i just cut apart the filter and some bearing chunks found their way in their in there. I guess im not sure its a main bearing but its definately in the bottom end. also last year i ran valvoline race oil 20w 50 (high zinc) and made the switch to amsoil this year. could i have a compatability issue? it ran 500 miles this year

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Your oil didn't cause this....i agree with bomber, a good slow inspection at disassembly should reveal the root cause. I used to do all the warranty work on commercial lawn equipment engines and we had to document everything to submit a claim. What i'm saying is take your time to find the cause so history doesn't repeat itself. Let us know how it goes and some picks can help everyone learn something in the process. Good luck, Rick