I honed the bores till the bores had no lips on the top and checked the new piston ring gaps which were within the tolerences in the Haynes Manual.

When I pull the cap off with the engine running it tries to cut out.

Up to 15 PSi it is fine right they way through the rev range.

Gonna do a compression test at the weekend just to double check everything.

Does anyone know what the standard breather setup can handle?

Cheers
Dave