Genuine BSA piston rings.

[Smoothpierre]

Hi, I have secured a set of genuine OEM piston rings for my B31, these rings have the overlaping ends - What would be the ring gap for this type of ring??

[AdrianS]

2 - 3 thou per inch of bore is the usual recommended figure. Put a ring in the barrel at the tightest position and measure the gap between the ends of the outer part of the ring

[Smoothpierre]

Thanks Andy for the info, but these rings that I have are angle cut at the ends, thus they overlap and although they should provide a good seal under normal circumstances but, I have measured about .050" + on these particular rings - seems excessive to me. I hope you can picture what i'm saying, these are OEM NOS BSA rings. Its like two backslashes together only a much shallower angle. //
         

[AdrianS]

The gap is present to allow for expansion so the piston/rings don't seize in the bore. Also needed somewhat for lubrication purposes.
Put the rings into the bore at various places in the bore and see how much they compress and try to measure or make an "accurate guess" of the gap. As I said before, 2 - 3 thou per inch of bore used to be the norm.