Piston ring size

[Clarks3]

Hello I am restoring a 1953 165 CC Harley Hummer and I am still new to this my question is regarding the piston and rings.
On the top of my piston it is marked with 4 also a B and STD I have to sets of piston rings one set that is.040" and is way too big and the second set is .020" and is also too big.
Curious if anybody knows if the .010"rings will work?
Thanks.

[250_Sprint]

You can measure the piston and determine if it is a standard size.

[Mutt]

.005 rings will most likely work

[Clarks3]

Thank you both for the much needed information I will try out the .005

[Backyard Bob]

Be sure and check the ring gap when fitting the .005 rings. Mutt, what should it be?

[Mutt]

It should be .012"-,020" Chances are since the bore is already worn, that wont be a problem

[Clarks3]

Would anybody have any ideas where I could locate a set of .005" piston rings I am only able to locate .010" and up?

[Mutt]

I'll look. I remember seeing some NOS .005 rings in the parts room but dont remember which model they are for

[Clarks3]

Okay thank you that would be helpful.
Also are you allowed to file them to size I noticed in the service book it says not to do so, just curious if it can still be done if needed?

[Mutt]

I doubt you will have to file them, but yes, nprmally with a fresh bore you have to file them to get the correct end gaps