99% of the time surging with a governed engine is because the air: fuel ratio is too lean to maintain a constant speed
So either not enough fuel is getting in or air is entering the engine after the fuel is added by the carburettor .
Floating debris builds up in the fuel tank and gets pulled into the fuel outlet by the fuel flowing then floats away the instant the engine is stopped .
Some think cleaning a carb is just squirting some carb cleaned down the throat ( does nothing ) or removing the float bowl and tipping the accumulated crud out.
Proper cleaning requires a full strip down, ultrasonic cleaning, dip cleaning , boiling the reassembly with new service parts .
