goodo , i just aquired another even older mayfair that seems to have a simmilar problem to yours. starts fine then sounds like it runs out of spark ! havnt really looked at it yet though , just made sure nothing was gunna fall of when it did start . never seen one the same before so when its light i'll show you . best i can see its 1966 impulse starter and handles i've never seen before . but sounds the same problem ! runs fine for a few min's then gets weak and wont rev and finally stalls out . dull spark

i'll let ya know