Do you have a compression tester?
Do you have an adapter for a 12mm plug hole?
Since most of the wiring harness is not connected to anything, you will need a spare battery and some cables....or a jumper box.
Take the spark plug out & install the compression tester.
Place something in the carb throat to hold the slide open......or just take the carb off.
Connect the positive cable to the threaded bolt on the starter, connect the positive cable to the battery, connect the negative cable to the engine block or some good ground on the frame......then hold the throttle open if the carb is still non and then touch the negative cable to the negative battery cable and watch the pressure gauge. It should jump up to a number over 100 within a few turns and stabilize with a bit of bouncing each time the piston reaches TDC. Once it stabilizes that is the compression number.
For $ 100......it is worth buying even if the compression is low.....the starter alone is worth that.
Dave
Where the heck is the rest of the frame?