Throttel

Sounds to me like the throttle cable is out of adjustment or wrapping itself over the throttle.I have seen this a lot if you have loosened the adjustment and jam nuts on the throttle cable itselt to remove the carb. Best thing to do is to try and loosen the tension on the cable and see if that first lowers the idle speed down.I would then inspect the portion of the throttle assembly that the cable goes into look to see if when you accelerate, the cable is sliding out of the throttle and catching on the throttle itself. Hope that helps you out