If this has been sitting this long, I recommend several things. 1.) reset the timing and check the thermo dashpot. It;s supposed to advance when the ngine is warm, but the rubber diaphragm is often seized after 30 yrs. 2.) overhaul the carb... or if you can afford it, replace it. Replace the thermostat & flush the cooling system 3,). Either drop the gas tank & clean the hell out of it, or run 2 fuel filters in line to catch the crap that's gathered from sitting.