Are they complete? If not, you will need to get out your checkbook. You'll need an electric starter, motor mount, depending on what these were raced in you could need exhaust and attachments and a clutch.
Clutches or jackshaft?
First rotate the crank listsen/feel for noise or scrapes.
Check for loose bearing by raising or wiggling the crank verticaly.
Next look through the exhaust port for signs of scoring , broke ring or burn't piston .
After that you can start them or pull head for further inspection of cylinder.
There should be a small rectangular piece on the chain guard typically .
It's your ignition box/device .
Simple little engine.
Carbs may need rebuilt , pulse line from crankcase to carb needs to be connected.
8 ounces of oil to the gallon .