2 3/4hp valve cap sealing washers, which way round, or doesn't it matter?

[spency777]

Hopefully this will be an easy one for all you experts.
I've just bought a set of four new valve cap sealing washers from the spares scheme for my 1924 2 3/4hp TS. I've noticed they have a flat side and a half domed side, anyone know if the flat goes against the cap or the cylinder head or doesn't it make any difference?
Also does anyone know what kind of PSI I should be getting with a compression tester? The bike runs OK but (to quote the reproduction owners manual) seems to have lost some of its "vim and vigour"!

Many thanks to you all,
Richard

[cardan]

I haven't seen the club rings, but I doubt it matters too much which way they go on. People may have their own preferences to aid sealing, but I just use oil on the threads and gasket. Smokes and bubbles a little at first, but usually seals itself after the first run. Make sure you have a close-fitting spanner, and retighten once the engine is warm. Just pull the bungs up "tight" - no need for anything drastic (like a hammer).

Leon