Gas will not flow from tank to motor while running

This sounds likely a badly routed fuel line that is getting hot and causing airlocks. The fuel delivery is slow, the gas heats up and vaporizes causing an air lock. You can test by removing the fuel line and with no engine running, run the contents of the fuel tank into a container. Do you have good fuel flow?

Or the float bowl isn't venting via its overflow pipe.

Sounds like it might be starved for either air or fuel. Have you made sure there is full gas flow from the tank to the carb? Also recheck the needle valve regulating gas flow into the carb. May be that a speck of trash is partially plugging that flow to carb. Should have in-line fuel filter (add on) in addition to the bowl 'filter

David the fuel filter in the tank has become clogged. It needs cleaning.

Ensure fresh gas is in tank. Follow gas line from tank to carb. Have locking pliers ready to pinch off gas line or close gas line valve. Remove gas line from carb. observe gas flow to carb. Remove carb bowl from bottom of carb. Attach gas line to carb. Does gas flow to carb. Observe float, float down gas flows, float up no gas flow. If float is bad replace float assembly or carb. Remove float mounting pin and needle metering valve. Use a bread wrapper pealed back an inch so thin wire can clean out port of meter needle. Use wire to clean out center port. Observe bowl screw look for hole thru screw, clean out with wire if preset. Re-assemble carb. Clean replace air filter. Fill oil. 30w. Prime motor, pull rope 10 times to start. No start, replace carb.

This is sometimes caused by dirt or debris in the fuel tank, carburator float bowl or in-line fuel filter if it has one. When you start the motor the dirt is settled down and the motor runs fine. While the motor is running, the vibrations and fuel flowing through the system agitates the dirt and it eventually plugs the filter or jets. When the motor shuts down the dirt settles down and the process repeats. Replace the in-line filter if it has one and clean out the float bowl on the carb. While you have the fuel line off, let some gas flow through the fuel lines to flush them out. If dirt is a problem also check your gas can(s).

if you have gas to carb rebuild carb or relace

Hi,
Just a suggestion O.K?
Carefully check the small fuel lines. To and from the bulb. Make sure the bulb fills with gas.( at least two thirds full. ) There is a small fuel filter on the end of a small fuel line in the tank. A small hook of stiff wire will dig that out. Good luck !!!!

I had the same mower in my shop with the same prob. Last week, here is what i did to correct the problem, take the fuel line apart at the fuel filter, open the fuel cap and drain the gas from the tank, once it stops i took couple old walmart bags and compressed air to slowly blow air in to the tank to blow the residue and trash out of the fuel tank. Next using compressed air to blow through the fuel line from where the filter was toward the carb. Next unbolt the carb and remove the fuel bowl, take the small pin holding the float out and slowly remove the float pulling strait up as the needle will be attached via a small channel on the float. There is where you will find the seat which the needle you extracted sets in to stop or allow the fuel to flow. Clean these parts and area WELL. i usually take the air screws out and use carb cleaner to clean those areas as well. Reinstall the needle and float, pin assembly and the bowl. Reinstall the carb , and make SURE to install a new fuel filter not exceeding the last filters micron flow, double check all connections, clamps, and hardware, add new FRESH gasoline with no less than 89 octane at any time, engine should fire and run as intended.

Check in line filter, if none, pull the line off at the carb, if no gas flow, blow into the tank to remove the restriction. If the tank is full of rust, remove it, dump out the gas, fill the tank with sharp rock pebbles the size of peas to a 1/8 inch of the bottom. Shake the pebbles around in the tank till all the rust is loosened. Dump out the pebbles, wash the tank throughly with water and pour out on a white rag until all rust and pebbles are not visable on the dump rag. Dry the tank in the sun, then reassemble. Remove bowl on carb to acertain fuel flow to the bowl, and it is also clean. If motor still runs inconsistantly, drop the center nut again that holds the needle jet, this should clear the problem.

clean carb bowl