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BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: watts on 10 May, 2025, 11:16

Title: BSA M21
Post by: watts on 10 May, 2025, 11:16
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
Title: Re: BSA M21
Post by: ducati2242 on 10 May, 2025, 17:38
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 .
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