Hey guys,
Whats the piston rings original part number please?

Greetings from Tennessee. 
   Do you need standard, first oversize rings etc? Tell us some more details also there probably is a parts list in the tech library also a 72 is a CT2 check your vin in the library 

Hi,
it’s a standard size. 

 from Salisbury, UK, Dugadie.

First thing is to pin down exactly which model you have - check your engine and frame numbers against the VIN tables in the Tech Library (see top toolbar). The numbers would originally have been the same, but previous owners might have mixed and matched them over the years.

A 1972 model will be a CT2, although the frame number will commence CT1.

As well as the parts lists (and manuals!) that Ht1kid mentioned, CMSNL and Partzilla are great sources of parts and parts information.  

Thanks, I believe the ct1,2,3 in 1971,72,73 shared the same size piston and rings cause the jugs and top end were exactly all alike 

My vin on the neck reads Neck vin : ct1-089189
 

Looks like a 1972 CT2 in Brilliant Red. Is the engine number the same?

The 1972 and 1973 CT2 and CT3 had reed valves, the earlier CT1 did not. The cylinders are therefore obviously different as, I believe, are the pistons and rings. However, wait for others to confirm. 

Yes mine the brilliant red one has reed valves 

316-11610-00-00

The parts diagrams can be a little confusing as they combine the 125s and 175s. I just finished a CT3 and the piston should be the same and should start with 314. The part # that starts with 316 is the 125. If you are replacing the piston pin that will be 251-11633-00, they also list 137-11633-00 for the 125. Ask me how I know about the pin, I have a 137 pin in the parts bin now.
Cheers