If the engine will run all day at partial throttle, but quit when you advance the throttle to full, it sounds like a fuel delivery problem. You may need to disassemble the carburetor to see if there's any kind of debris that would interfere with high-speed fuel flow. One problem could be an idle needle that's just too lean. If it's too lean, then it will interfere with high-speed fuel flow. Richen it a LOT, start at part throttle and see if you can get the engine to full. Get the top-end leaned and then go back and work on the idle.

If you can't get the engine set at all, you may have a problem with the piston/cylinder fit, although the idle usually goes bad first when you start to lose the compression fit.

If all else fails, the engine can be sent to the service center to be checked out.