Jason, please do the test I asked for on fuel flow through the fuel line. Disconnect the line at the carburetor, and let the fuel run into a cup. See whether it continues to run at full flow, or can only sustain a trickle. Continue the test for at least a cupfull of fuel, preferably more.

I am trying to check two things here, either of which could cause your problem. The more likely of the two: the vent in your fuel tank cap may be clogged:
[Linked Image]


Cleaning that vent should be a routine service check.

The second thing the flow check will test for, is an obstructed fuel filter or one that has been installed backward.

The reason the clogged tank cap is the more likely problem, is that it takes half an hour's running for the engine to stop. Given that you said the tank is about 3/4 full, it would take a while to create a decent vacuum in that amount of air space.

Last edited by grumpy; 16/01/13 02:33 AM. Reason: Add detail