We have a H500 with lateral shake on stick, there is NO shake in fore & aft plane.
Both trim motor were shot! both replaced & correctly adjusted.
All head bearings worn & replaces same with droop stops.
Swash plate bearing good 6 months old.
No wear in pitch link or rod ends.
With no blades on the head is staring (after balancing).
We tried another head, swash plate & bearing , (This head & SP was perfect on the one we removed it from) the shake was still there it is only lateral about 1\2inch but there at ground idle & in flight, cant feel it through pedals but there is a slight drumming you can feel in the hull, but does not seem to be in sympathy
Checked pylon bolts & pylon for any visible damage, gear box mounts.
Engine mountings\ alignment, OK short shaft,OK tail rotor drive shaft OK.
The stick shake appears to be in time with the rotor speed RPM
Driving us to drink any ideas.