Piston rings for Jahns pistons
 

I have a smoking problem but hardly any blowby and when the head was off no cylinder damage or wear was evident,the pistons are .040 oversized.
It was sitting for many years and at first there was puffing blowby until it ran a while then it stopped,the compression is even and all cylinders get oil on the plugs but not enough to foul them the ceramic is deep up in the X plugs and burns a light brown,the valve guides are not loose so I figure it is a oil ring problem.
I don’t see any listings for the aluminum jahns pistons.

Re: Piston rings for Jahns pistons
 

search for OTTO Machine. He would have rings I bet.

Re: Piston rings for Jahns pistons
 

If the Jahns pistons take the narrow compression rings and wider oil control rings, the Hastings or Grant will work. Just different material between the two brands.
Langs Snyders and other supplier should have them but check before you order, there are some sizes that have been out of stock for a while.