Hmmmnnm,
Sort of sounds like the crank seals are bad. Pull off the l.h. side cover and grab the mag flywheel with your hand and try to detect any movement up/down, left right, in/out by feeling for a "slight click". While you are there look at the area around the mag flywheel , especially below it for any signs of moisture. Any signs of wetness indicates bad crank seals and any "click movement" felt in a non-rotation movement indicates bad crank bearings. Both will make it hard to start and on a short fuse to destruction.
Otherwise, make sure you are using the choke and not turning the throttle. The choke on those models is a fuel bleed circuit that is eliminated when the carb slide is raised by the throttle. Also, make sure the carb slide is completely bottoming out. I have seen many that were put in the carb body backwards and many that had the cable adjusted too tight to let the carb slide bottom out.
AND make sure you are using a NEW spark plug.
OriginalDirt