Get an OS 8 glow plug to eliminate one possible source of problems. Also make sure that the fuel lines are O.K. with no air leaks. Even microscopic leaks will cause tuning problems. There should be no air bubbles visible in the fuel line.

In general, once the engine has been properly tuned there is little need to fiddle with the carburettor.
At most one has to adjust the main needle a couple of clicks either way to compensate for temperature/humidity changes, but no more than that.
As you may have noticed engines tend to lean out once in the air. My advice is to tune your engine slightly on the rich side on the ground.
If you don't have it, download an engine manual from [link=http://www.osengines.com/manuals/index.html]http://www.osengines.com/manuals/index.html[/link]. It will tell you how to properly tune your engine.

/Red B.