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Makotosun

Top of piston identification marks

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Replied by retro on topic Top of piston identification marks

I have a JT1 with a "96" on top & another with a "42 25" on it. What do those numbers mean? Thanx Much!
22 Dec 2020 08:08 #11

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Replied by MarkT on topic Top of piston identification marks

Posting photos are always a good idea but in general the 96 is a standard and the 25 is first over.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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22 Dec 2020 08:28 #12

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Replied by Bdee on topic Top of piston identification marks

Curious what these numbers mean. From a CT3

22 Dec 2021 21:49 #13

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Replied by MarkT on topic Top of piston identification marks

Arrow points to exhaust port.  Numbers by arrow are likely some kind of manufacturing, inspector, or batch code. 

The 975 should be the original size grading for a standard piston.  Standard bore on a CT is nominally 66mm so piston would have measured 65.975 mm when new.  Cylinder might still have inked code on skirts that are down inside case...  the 975 and size code on cylinder were used at assembly to select parts and end up with the correct piston to bore clearance when first assembled.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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23 Dec 2021 06:03 #14

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Replied by Bdee on topic Top of piston identification marks

Thanks so much for the info!
23 Dec 2021 09:36 #15

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