Suggest look for a reason the fork isn't pulling back the aprox 1/8 inch at idle, like it should. It may have slack up to the fork base, or it may be all the way back hitting the housing. Either one would give the high revs.
Check that the fork isn't pinned on backwards.
I put one on backwards, and it fits on, and puts the arms more twards the carb, than when on correctly. 1/8" punch will drive the tapered pin out, after unscrewing the oil line fitting.