I have a 1953 Golden Jubilee that has always had a very slight missfire. sort of a puffing at the end of the tail pipe. She Uses no oil...No smoke. I replaced the distributor with a new one. New coil...new plug wires. Set the timing at 8 degrees BTDC. New Sediment fixture...New 12 volt resistor (my tractor is a 12 volt conversion) new ignition switch...It runs better at fast idle. I tried Seafoam...Tractor has plenty of power