The S-620 is one of those old single stagers with the straight blades and
the little rubber vanes for directional control and a 2-stroke-cycle
engine.

What kind of governor do these things have? Is it a little flyweight thing
inside the engine or air vane or something else? The reason I ask is
because I have one that starts and runs ok but wade into any snow and the
speed drops to the point of stalling and seems to be running on a fixed
throttle. I took the cover off and tried to watch for any movement of the
throttle and there is none so that's kind of confirmed but not the reason
why. It's got the spring tugging the throttle in the open direction and
the little wire link coming from points unknown. If it's an internal
engine part then it's not really worth fixing on such an old machine.