Yo, I think that if you have spark and there is some suction at the carb, then what may be happening is the fuel is being interrupted between the carb and the piston. So, drop the engine down a little bit (I've got a QT50) as it might be a little tight for your hands. Take the carb off completely and remove CAREFULLY the intake manifold thingy that it hooks onto. Underneath you will see some thin metal reeds attached to a plate that exists between the carb and the piston chamber. Mine was completely fouled and caused untold confusion and frustration until I cleaned the sonofabitch out. That might make the difference.
P.S. How do you know that there is plenty of compression?