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O.S. 1.20 AX rebuild

Old 07-28-2015, 05:35 PM
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dbacque
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Default O.S. 1.20 AX rebuild

I have noticed my 1.20 AX is feeling weak in verticals. Compression also feels low. I figured it was time for a ring and cylinder sleeve.

When I disassembled the engine, I found the ring was broken and the piston heavily scored. Okay, I need to order a new piston too.

I thought this piston had an arrow engraved into the top but it's all invisible at this point, the engine has LOTS of time on it. When I get the new piston, what is the correct orientation?

This engine has been magnificent. It's a powerhouse and I've gotten more miles than anybody has any reason to expect from an engine. I'd just like to make sure that I rebuild it correctly so I can do it again.

Thanks,
Dave
Old 07-29-2015, 06:52 AM
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Bax
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There is a pin in the piston's ring groove that locates the ring gap. You want the ring gap to be on a web. That's usually between the aft intake port and the port directly opposite the exhaust. Once you examine the piston, it becomes obvious.

Last edited by Bax; 07-30-2015 at 05:52 AM.
Old 07-29-2015, 02:16 PM
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dbacque
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Exactly what I was looking for. Thanks Bax!
Old 05-30-2020, 04:18 PM
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acejinx
 
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Default Great!

I needed that answer also! Thanks. Such a great engine.

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