I was given an Enya 60X engine that I was told was only bench run but never flown.
It’s very clean and looks brand new.
Smooth turning with good compression.

It starts immediately when primed but won’t continue.
I tried choking it with my finger and noticed it’ll only draw fuel when the throttle is 80-100% open but at lower throttle you only hear the hissing of air entering through the air bleed hole but it won’t draw any fuel.
The air bleed screw is set so that it closes half the hole, probably set that way since it was assembled.

What can be wrong? Why won’t it draw fuel?