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Decode letters/numbers on pistons

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58Custom

58Custom

Jedi Warrior
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I just pulled the head off of my 1275. The cylinder measures roughly 2.80 with my calipers, so I guess it's been bored .02 over if my manual is correct. The pistons have the following stamped along one edge:

Top 0015 X1

I pretty much have "top" figured out, but what is the meaning of the other marks?
 
LOL, can't be a 15cc dish, you know how big that would be. Normal is 6cc.
 
Well, it's not critical, I was just wondering. The cylinders measure .02 over. I took it all apart yesterday and every piston had broken top rings, and a couple had broken second rings. I think that possibly was the source of my excessive blowby.

Cylinders do not look too bad, so I will berry-brush it and put it back with new rings and bearings and get to driving it.
 
Last I remember your measurement of the bore was a "rough measurement". You might want to confirm that measurement before proceding to buy parts, etc.
The X1 is definately not first oversize. That would be marked something like 010. The 15 might be a part number for an oversized piston.
 
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