If you found such a nozzle you now mount a smaller nozzle until the engine under full load no longer stutters.
This means that you already have an ideal basic nozzle that ensures that the engine does not receive too little fuel under full load, which it also needs to cool the piston and cylinder. A safety optimum represents an engine adjusted in such a way, which throttles completely easily briefly if one closes the gas again under full load.
Arreche, a Spanish manufacturer of carburettors and carburettor accessories, produces after classical type of carburettors of Amal and Mikuni (under license).
Thus hexagonal main nozzles are used in the Arreche carburettors, as they are used in quite similar construction form also in the modern Mikuni TM/TMX carburettors. Among other things, they are incompatible with each other due to the different threads.
The Arreche nozzles are graduated in five steps, e.g. 60, 65, 70,,