On the HS2 carb, how far do I push in the piston lifting pin when checking the mixture? All the way in, or just part way?
If I push mine all the way, the engine tends to cut out.
After you have taken up the obvious 'free play' you should only lift the piston about 1/8 - 3/16" inch. If revs rise then too rich, if revs fall then too weak - if they stay much the same - then just right! Be sure the engine is fully warmed up when doing the check.
Remember this is just the idling mixture - has only a tiny effect on the actual 'running' mixture.