Hatori fitted, cannot comment on the difference, issues with OS55 HZ-R regulator nonsense, running rich, regulators sticking open, in fact two yesterday despite fuel filters every where, no crap found within.
So last night, removed all the -R crap, fitted a HZ main needle seat and fuel inlet ring, clamped up the crankcase pipe and wow, its a different heli, engine easy to tune with plenty of power and no tantrams to deal with