Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Is it surging under load while mowing or just running n load? Can you stabilize it by touching the linkage? On the linkage will be springs, take all the slack out of the springs, but do not add any tension, just get the slack out, and see if that doesn't take care of the surge. You did check the fuel solenoid in the carburetor for full movement and it is not binding?