Any advice is welcome. I'm in the process of rebuilding my banshee motor. I'm just about done, I've got the pistons left to do. I have stock (standard) pistons. I ordered a set of stock (standard) piston rings from bikebandit. I put the rings on, and they were way too thick.
I measured the pistons and rings with a micrometer, and this is what I came up with:
The piston diameters measured 2.515". OK. I checked my Clymer manual, and that is the measurement of a stock piston.
BOTH the old rings measured .038". The new rings I ordered measured .047" and .058". I put them on, the thicker one in the top ring slot, and it was obvious that they were incorrect.
I cross-referenced the part number on the piston ring box, and it shows up correct, that they are standard size piston rings. I just don't get it. Why are these rings not the right size? Why don't they fit correctly in my pistons? Is there any way to cross-reference the stencilled numbers on the tops of the piston domes?
I thought maybe somebody put the wrong rings in the box at the company, but both boxes? Unlikely.
There is a possibility these aren't stock Yamaha pistons, cause I bought the bike used, but they sure do look like stock Yamaha pistons. I'm really curious about the writing on the tops of the pistons. Anybody got any hints?