Tecumseh engine help

Hello everyone i am having trouble with my Tecumseh lawnmower. The engine starts and runs but surges and sometimes cuts out. Ive took the head off and the inside is full of carbon build up round the valves which i am going to clean, I tried cleaning the carburettor before but the engine still surges and runs high. Ive also noticed that the rods on the carburettor move as the engine surges.

Any help would be great.

Thanks James.

Tecumseh engine help