RE: Beginner speed?
You know, I just got to thinking, if you cant adjust the engine even on the ground and you tried new fuel, glow plugs,bearings,not foaming, tightened the case and head screws (obviously, you just reassemble it).
One thing I know can cause an engine to hunt or to cause you fruitlessly chase a high speed needle setting is a leak between the crankshaft and the crankcase. The fuel momentarily fills the void and seals, than gets drawn away and the cycle repeats. This leak or excessive clearance can be caused by debris from bad bearings, dirt ingested or it was made that way, this is very rare but I have personally see it in a well known performance engine with a total clearance of .0075" out of the box!
If this is the case. the engine is junk.