MTD gallop

First you need to find out if it is the governor or carburetor that is the source of the problem. With the engine running and loping find the throttle vane of the carburetor and hold it steady.
 
Now does it stop the loping or does the engine dies? If stops then you need to do a static governor adjustment or otherwise it is the carburetor that needs adjusting or cleaning.

With the engine stopped, loosen the screw holding the governor lever to the governor shaft clamp. Push the
governor lever to move the carburetor throttle plate to the wide open position and hold. Watch which direction this lever moves to open the throttle plate wide open as you will need to rotate the governor shaft in the same direction until it stops. Then tighten the governor clamp screw without allowing things to move before the clamp is tight.