BSA M21

[watts]

I have had trouble starting it, I did a compression test. 25-27psi.

I suspect that is a bit low even for a SV!

Thanks
Matthew

[ducati2242]

Think you need to renew the rings and grind the valves in . should be between 80 and 100 psi not the greatest even then but at 4.5/1 its as high as you can expect .