I don't suggest running motors that are sitting on the ground. We had an incident with a small block that you don't want to repeat
At minimum you will need the motor on a stand, this is google-able.
You will need the coils, plugs, spark plug wires, and a switch to turn them on and off. All gets wired to the ignition system on the motor.
Beyond that you should check that the motor will turn over, check if there is any oil in it, and what condition it is in. This may give you some info on the bike's history. 750s use a "dry-sump" oiling system, thus the oil is contained in an external tank and circulated through the engine, not stored in the engine like conventional cars etc. I would not suggest running a motorcycle engine with no oil supply. The oil supply lines use special fittings, but I believe that you can use regular hydraulic hose and high pressure clamps to make your own hoses if the ends are there. also change the filter if it hasn't been run in years.
Wiring up the starter with a high amp relay or large contactor.
Fuel supply is not difficult. If the tank is in good condition you can use it, just make sure that it is above the level of the carbs, because they are gravity fed. Make sure that you have a valve to turn the fuel off in case of leaks, don't burn your house down.
I would check the compression on the stand if possible, I believe it is a pain to get the fittings in once installed in the bike.
Finally check visually inside carbs, make sure no one is living in there, that the slides operate and return.
Some form of exhaust would be advisable, but not strictly necessary if you just want to hear it fire.
Now having said all that, without properly setting up all these things for some actual running, you won't learn anything about the condition of the motor. 90% of motors with no history will fire if you hold a gassy rag on the intake. Some of them will have blown rod bearings, missing parts, bent valves etc. And of the 10% that don't fire, most of them have wiring problems.
If you want to bench test the motor because you don't have plans to build the bike soon, then get a stand welded up, build a nice bench test rig with your ignition and whatnot, then see what you've got. If you want to build the bike for next season I would suggest just assembling it all to see what you are missing, then if you have motor issues you can assess them as needed.
Hope I helped.
Jon
