Hello everybody, just bought my first trials bike to refurbish, an Ossa 250 I think with engine no. M231638. I've looked online and all I've found are engine no's. beginning with B. I couldn't find a number on the frame. Any help much appreciated.

It's a 1975 250 MAR MK2, the engine and frame numbers are the same, just that the engine is prefixed M and the frame B.  The frame number is on the headstock, maybe hidden by layers of paint as the original frame colour is silver/grey with white tank/sidepanels and green stripe. A previous owner has painted it all green and black engine/forks to look like the 1979 version

Cheers Woody, that's a great help, now I know year for spare parts etc.

Thanks again,

Best regards, Colin.

While I'm on , can anyone recommend a good spares supplier in the UK please?

Thanks, Colin.

In Motion should have most of what you need   https://www.inmotiontrials.com/