I have a JT1 with a "96" on top & another with a "42 25" on it. What do those numbers mean? Thanx Much!

Posting photos are always a good idea but in general the 96 is a standard and the 25 is first over.

Curious what these numbers mean. From a CT3

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.

Thanks so much for the info!

Hi All,  

Pulled this one apart tonight,  carbon fouled top..   little scuff revealed this number.. im guessing standard bore for 70, 360, RT1.  Book shows 4 standard pistons, 79.96, 79.97, 79.98, 79.99 before they go oversize..

Do these numbers ring any bells? Just curious,  they mean absolutely nothing to me.. 

Im guessing, from the amount of carbon build on the top of the piston and the head, there was ring failure.. the cylinder looks pretty nice but… could still have issues that a bore gauge will have to sort out and a mic on the piston. 

Thanks,
Drac

hope this link below works 

drive.google.com/file/d/1kg2LAe78jydm3-c...GK/view?usp=drivesdk

It asks for permission to access the picture.

Pic is the best.  Or at least mention the numbers you're seeing.