BSA B40 3.50cc 1965 piston ring

[zak]

hi how are you  my name is alex ,thanks for add me to the group
i have a BSA B40 3.50 cc  1965 and i want  to replace the piston ring with new one  can someone help me with a shop  please
my mail is 6228zak@gmail.com
thanks

[Rog1]

Zak, where are you?

[zak]

hi
i am in Cyprus

[Spaceman]

Any idea what size the piston is to determine what STD or oversize ring set you need? The size may be marked in the top of the piston otherwise you would need to measure its diameter.

[zak]

is the standard size 

[Spaceman]

I don't know which source would be best to buy from Cyprus but I have bought bits from British Only Austria in the past and they do a STD B40 piston ring set:

https://www.vintage-motorcycle.com/en/parts/bsa-piston-rings/bsa-b40-piston-ring-set-std

[Spaceman]

It's probably worth asking why you want to replace the existing STD rings with a new set? I assume its because the ring gaps have reached the wear limit of about 25 thou (0.625 mm) and you are hoping new rings will bring this back into spec? Hopefully, it will do but you have to be careful to ensure that the bore itself is still within acceptable limits. Each thou of bore wear will add 3 thou to the ring gaps and therefore you probably need to ensure the wear in the bore diameter is much less than 5 thou (0.127 mm).

[zak]

the engine has not be open from the day that came to cyprus
thanks all of you for the support 
i will sent you photo when i will finish