I have a Thunder Tiger 91 four stroke. I can't get it to run for more than a few minutes. The Choke plate is installed, the fuel tank and system are ok. Have been persistent and have got a gallon and 1/2 fuel through it but situation hasn't improved much. If I run it real rich where it doesn't produce much power, it will keep running. Lean a little and after a short time it like seizes up. Anyone have any suggestions before I send it in.

Don