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Discussion Starter · #1 ·
Hi,

I'm having my '97 RD07A engine rebuilt since the output shaft bearing broke (the bike has done about 120 thousand km). I'm now planning to replace all the bearings, cam chains, tensioners, output shaft.

BUT, it also came out the pressures in the combustion chamber are out of limits. It looks like the oil ring has stuck at some point and damaged the cylinder. Since I bought the bike as used about 10 years ago, and it seems someone has opened the engine before, I can't really be sure that oversized pistons have not been installed already. So, how do I tell if current pistons are standard or oversized? I can't find actual measures for pistons and cylinders anywhere, the Honda catalogue just states "std", "0.25" or "0.50", but no actual measures. Do oversized pistons have some kind of markings on them? Or anyone knows what is the size of std piston?

Thanks,
r.
 

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Standard pistons normally have "std" stamped on the top. Oversized pistons normally have +.25 or +.50 stamped on the top. Standard size is 80.97mm to 80.99mm. So first oversize will be .25mm larger, 81.22mm to 81.24mm. Second oversize .50mm larger 81.47 to 81.49mm. Hope this helps.
 

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Discussion Starter · #3 ·
Thanks, exactly what I needed. I actually found those numbers now from the Haynes manual as well :)
 
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