did you free up the governor? Take it loose from the throttle lever on the carburetor and work the throttle by hand? Back out on the idle speed screw all the way?
you can control the speed of the engine, the problem more often than not, is to get it to run at the low speed or pull the main engine at high speed😄
if closing the throttle doesn't slow it down, apply for a patent, you're sittin on a gold mine