Microlite 2.8 in our ‘97PW will start fine, run for about 5 minutes then quit. I exercise it monthly under load for two hours at a time. Use Seafoam in main gas tank regularly. Seems like it wants ...
I replaced the fuel pump (common failure item), and the filter. Seemed to help for a bit. I tried the high concentration SeaFoam mix. Didn't help. I ultimately replaced the carburetor, which has it running like new.
Shame they don't sell rebuild kits for their carburetors.