The head gap where for both engines with 25% fuel with measured 0,65mm gap. I removed or put a 0,1mm head shim when i changed the gap.

Some courios thing was with the engine with died and i can not restart pumped no fuel in the line. Only when close exhaust he gets fuel for a moment. With one shim more it was no problem.

That is what i not understand because normally you remove 0,1mm shim and engine is running with 16% EU fuel.
The only difference was the carburator. One has a lying needle and one needle is standing but i cannot imagine that this makes the difference.

When i compare it with othe engines (Ielasi OS engines turn higher that my nova and they always was great with 25%.

Fuel is the same manufacture and i used the same fuel which the OS guys use.
Maybe it is the exhaust which the Ielasi OS guys use because they have some special pipe which is very thin towards the manifold.