Cub dies after 20-30min

[Don McCombs]

My next investigation would be the condensor. Not very expensive to replace. Even better if you have a known good condensor to swap it out with.

[muleboss]

Have you tried pulling choke as it dies. I am thinking fuel as in trash in tank and when it dies it releives suction pressure and trash moves from over hole. Just a thought.

[Glen]

Hi,
If the vents in the gas cap are plugged, it would probably make the gas stop flowing to the carburetor in about the time you said it stops running.
The gas cap should be vented.
When it stops running, you could loosen the cap and listen for any vacuum sound from the gas tank.
There should not be vacuum in the tank with a vented cap.

Below are pics from TM Tractor of the original style gas cap used for years on Cubs.
Look at your cap and clean the vent holes with a small wire.
There is 1 hole at the top, and 2 holes on the bottom, near the gasket.

http://www.tmtractor.com/tm-tractor/gfl/fuelcap_001.htm

The coil could be quitting also.
I would replace the condenser first, it costs less than the coil.

[outdoors4evr]

If you do have a gas cap like Glen linked to, then please consider getting a new free one that is less likely to catch fire.
https://www.ihgascap.com/index.aspx

[Greg]

Thanks for the suggestions; I have tried loosening gas cap as it is dying, with no effect (I have teh new type gas cap). I'll try the condensor-- coil looks really expensive!