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opps, marked underside of crown with centre punch

Practical Engine Building

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I started disassembling my 83 yamaha v twin engine before watching these videos. I marked the pistons under the crown with a spring loaded centre punch, so now after watching these videos I'm worried I have introduced a stress/failure point. I'm doing a factory spec rebuild, the redline is 6000rpm. should i replace the pistons?

You could grind out the punch mark using a die grinder or dremel-type tool. Why don't you post a picture showing exactly where the punch marks are located?

It's a relatively lightly stressed engine, if that's the red line, and unless it's in a particularely sensitive area and/or you had the spring tension on the punch would right up, it's most unlikely to cause a problem -a picture would help, definitely, though.

Not sure if grinding out the mark would help, as material removal may cause more problems than leaving it as it would thin out that part of the crown and affect the stress distribution through the crown.

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