Hobbsy, spent six months on the corner of my work bench, then went to the scrap.

I did work out what was wrong with it. The Orings on the needle valve did not give a good seal, but the main problem was the O ring at the base of the carb split. I tried to replace, but split 4 more trying to get the carb back on, so gave up.

I know you like MDS, and the engine part is certainly powerful. The problem with MDS has always been the carb. Maybe the new carbs work well and are reliable, but no one in our club is willing to try, and all the LHSs near me no longer stock them as they can't sell them.

Second engine was an OS 25 LA. Still have that, and all engines since. The OS is sitting in an oilly rag full of after run oil waiting for me to get a suitable plane for it.