Change the starter as often as you like- - - - -it won't solve the hard starting problem. One more time- - - -check the primary ignition circuit- - - -ignition switch, coil, distributor wiring, internal circuit in the distributor, and the polarity switch. There's a high resistance connection that's hidden there somewhere. The reason the engine starts with the hand crank is there's no load on the battery- - - -more voltage available at the coil since the starter isn't stealing any of the voltage. I have fixed dozens of hard start problems over the past 65 years by finding the dirty connection(s) in the ignition circuit.
Jerry
