Problems with OS 40 FX
brudford
Sounds more like you have some drag in the throttle ,maybe dragging on the exit maybe even against the crankcase ,,but check it for the whole length, check all the anchor points if it is nyrod or cable in a sleeve , and the exit to see if there is flex or movement at the exit of the outer sleeve
Highlander
What kind of control linkage are you useing ?
Highlander