If I may interject a thought here....if the engine is changing RPM's up and
down, "like your moving the throttle stick" the setting is WAY TOO LEAN....
and the engine is surging. Usually when it does that, you have to open the
main needle about a 1/4 turn. If the engines is surging, it is overheating as
well, and can be damaged.

If you engine is surging in flight....always chop the throttle....bring the plane
in to land....and readjust the carb to avoid over heating.

FBD.