my dad gave his 1967 mac 10/10 machine of death which had your problem,alot of mower shops said its stuffed and to upgrade.i found that leaning off the idle a little and adjusting the wide open throttle fixed the problem.also how clean is the air flter and check the diaphragm in the carb...now mine starts in 2-3 pulls even when not used for great lengths of time,idles well hot or cold and revs like a demon!best of luck with your old gem...cheers sean
sean withers
August 2007