Stock Yamaha Pistons and Rings Problem

[RJames]

I'm in the middle of a restomod on a 1983 Heritage Special. I recently had the cylinders bored to the 4th oversize and bought NOS OEM Yamaha pistons and rings to match. The piston part # is 447-11638-01. One of the boxes I received had 447-11638-00, someone changed the -00 to -01. The Yamaha rings I purchased are part #447-11610-40.
Here's the problem. I'm having trouble getting the right rings on the right piston. The compression rings are different thicknesses, .405" and .506". I was able to match one set of rings to one piston that had different compression groove widths, but the other one has ring grooves that are the same dimensions to each other and the top compression ring has too much ring land play. Is it because the two pistons are different part #s, and their ring grooves are different?
I checked the ring gap in the newly bored cylinders and the compression rings are within spec. The oil control rings were nearly at their max allowances, and it seems that there isn't much tension to provide an adequate seal. I don't think I can purchase a larger oversize than 1.00mm, so I can't fit the ring gaps by hand. Any help? - Thanks

 

[650Skull]

Don't buy anything before asking questions..............https://www.cruzinimage.net/

and yes these guys have 6th oversize pistons and rings

 

[Bob Wegman]

I'm in the middle of a restomod on a 1983 Heritage Special. I recently had the cylinders bored to the 4th oversize and bought NOS OEM Yamaha pistons and rings to match. The piston part # is 447-11638-01. One of the boxes I received had 447-11638-00, someone changed the -00 to -01. The Yamaha rings I purchased are part #447-11610-40.
Here's the problem. I'm having trouble getting the right rings on the right piston. The compression rings are different thicknesses, .405" and .506". I was able to match one set of rings to one piston that had different compression groove widths, but the other one has ring grooves that are the same dimensions to each other and the top compression ring has too much ring land play. Is it because the two pistons are different part #s, and their ring grooves are different?
I checked the ring gap in the newly bored cylinders and the compression rings are within spec. The oil control rings were nearly at their max allowances, and it seems that there isn't much tension to provide an adequate seal. I don't think I can purchase a larger oversize than 1.00mm, so I can't fit the ring gaps by hand. Any help? - Thanks

Are you sure those are correct measurements you took? Seems really thick to me. I measured compression rings on a engine I have apart and my top ring measured; .046" and .058" for the second one.
Never mind I just noticed this is a real old posting. Sorry