The engine should run if the wiring harness is unhooked. It is a magneto ignition and the ignition switch grounds the circuit to kill the engine. Without the harness the circuit is not grounded and the engine will run. You will have to pull start it, but it isn't to bad. If you want use the electric starter, you could run jumper cables to the solenoid or directly to the starter
That engine has seen better days
It is a 71, as it has an adjustable Hi Speed needle on the carb, unique for that yr only
First thing, do a compression test, that will determine if you want to spend any more time on it. If good, pull the flywheel off and inspect the coils, the points, condenser, upper crankshaft seal(if wet with oil, it will need replacing).
Replacing the water pump impeller is pretty much a given, before running the engine.
Entire Fuel system will need some TLC, cleaning, inspection.
Initial settings for mixture needles:
Hi Speed - 1 turn out from lightly seated
Low Speed - 1 1/2 turns out from lightly seated