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Looks like you can be easily put back into spec. Tell us more about your set up.
Let us know what carburetor is on it. Tune it up and check the timing. Do you have a vacuum advance distributor? Is there a 4 wire plug coming off of it?
Since you don't have a gas analyzer it'll be important for us to know where your timing is to help you. Replace your plugs (gap them correctly), wires, cap, rotor, air filter, pcv valve, breather & fuel filter. Clean the carburetor and replace the fuel filter. When your done check the timing so you have a baseline as to where it was at before you try to adjust it. Let us know about that distributor.