[DBguy]

Sorry double post

 

[90 GP]

Assuming you have carbed engine check the dual diaphram unit on left side of carb. It has two speed settings ( one for deceleration and one for idle up with accessories on) . If any of the vac lines that attach to it are broken/missing it will elevate the idle to the speed you mention . Also check the choke butterfly to be sure it is opening wide when engine is warmed up.