Dave, I have perhaps got a bit confused by reading too many things - the instructions that come with my YSs, your invaluable help here, and the YS doctor site. I now have no idea when I should, and should not attempt to adjust the regulator!

On a normal engine, the idle needle controls the transition from idle to full power as well as setting a smooth idle. I had thought it was true also of the YS but now think I have got it wrong.

Is it correct to say that the idle needle on the YS only sets the smooth idle running, and that if the full power and idle needles are correct then any problems in throttling up are sorted by adjusting the regulator and not by adjusting the idle needle?

Harry

There is the very slightest of intermix on the needles, but you are correct in assuming that the regulator controls transition only.
Once set, the regulator usually doesn't have to be touched unless you change types of fuel, glow plug, or the weather changes drastically.