Basically gas is running down from the top to the throttle valves, then leaks out the shaft, or gasket.

PERCOLATION

• Percolation, or heat soak. Engine gets hot and then turning off the engine, the gas boils.
  • Try using different gas.
  • Make sure the engine isn’t running over normal.
  • Fuel line too close to the exhaust manifold.
  • Anti Percolator Adjustment
    • Crack throttle valve .030” between throttle valve and bore of carburetor, side opposite idle port. Adjust by bending rocker arm.

• After turning off the engine look down the bore. If gas is dribbling into the bore then the main discharge may be leaking. If it is then tap on the check ball lightly to form a good seat.