• Be sure the electrical system is up to par, especially the plugs.
• Heat from the engine may be causing the carburetor to percolate (gas boils). This allows too much gas into the intake manifold and until this is cleared out, the engine will not start.

HARD STARTING WITH COLD ENGINE

• To start press the gas pedal down once. This does 2 things. Adds an extra squirt of gas from the accelerator pump the cold engine needs to get started. The 2nd thing is pressing the gas pedal allows the fast idle cam to move to the high position against the idle screw. This allows the RPM to move up to 1800 or so RPM. Check that these 2 things are happening.
• Test the thermostat. Is it closed when the engine is cold. Remember that the gas pedal has to be pressed a bit to allow the fast idle and choke to close.
• Once warmed up the thermostat should be open.
• Check the choke adjustments – it could be the choke is choking off the engine.

HARD STARTING AFTER SITTING

The following are things you need to look at, not in any order:

• The float bowl should be vented. Follow any vent hole on the bowl cover to make sure it is clear.
• After turning off the engine look down the carburetor bore. If you see fuel dripping from the venturi then you have a leaking main discharge. The check ball may need to be seated (tap lightly to form a seal). Venturi gasket may not be sitting flat. They sometimes need to be trimmed.
• Percolation – After turning off a hot engine, the gas can boil out of the carburetor. You would most likely get a strong gas smell just after turning off the engine.
• Having the wrong gas cap can cause the gas to be siphoned. Putting a non vented cap when it requires a vented cap can be a problem.