R-5 piston marking

[dgorms]

 I just tore into the top end on my recently acquired 71 R-5, the bike presents as mostly original. I haven't measured anything yet. The marking on pistons is "970" in the back and "613" on one and"614" on the other (at front). The bores look good and minimal carbon on anything. I'm thinking standard, on original bore?....................................D

[SUPERTUNE]

Sounds like stock markings to me.
If an oversize you would see a .25,
50,.75 or 1.00 if were oversize in a oem piston top towards the intake side.
Chuck

[dgorms]

Thanks Chuck. That's what I thought. There is no other marks except the forward arrow. I did find an oem rd 350 piston in my stash that had "614" stamped on top. Well at least I know I'm dealing with std. bores......................................D

[rodneya]

My factory original dykes ring RD350 pistons had 614 and 974 on them.