This kind of thing is HARD to diagnose over the internet.But I have to ask the dreaded question: to the best of your knowledge has this tractor ever been overheated? If not, read on. If so, please tell us. Check that governor. It is easily done without dismantling anything. Check the fuel flow. You should see a steady stream of fuel come out of the line. If the fuel flow and governor look good, and the engine operation returns to normal EVERY TIME the load is removed and AS SOON as the load is removed, your problem is far more likely to be bad spark or compression (gasp!) than a carb problem. But the BEST way to eliminate the carb is to find a good running tractor similar to yours and borrow the carb to sub it out. About that ignition: the air-cooled Volkswagen community is the largest group of Petronix (sp?) users out there and they are SHARPLY divided over the reliability of them. So, replace that ignition switch first. You can also try checking the plugs for correct type and gap. (In my own personal experience the most common cause of missing under load and only under load is bad or incorrectly gapped plugs. But on the N series it seems to be the ignition switch.) Then, if all else fails, try subbing out the ignition. Unless the engine has been overheated. Then the odds shift away from spark and gas towards...
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