To check the actual ignition timing you can use an ordinary old-fashioned neon automotive timing light attached in series with the plug lead (gives red flashes, not very bright, no external power source required) or you can use a later xenon automotive timing light (attach power leads to a 12 Volt supply and just clamp a sensor around the plug lead, gives very bright blue-white flashes). Either way you'd need to locate TDC accurately though, then set up an external rotating protractor on the output shaft, unless there is some other rotating feature you prefer to use, such as the starting rope pulley. Note that the output shaft rotates anti-clockwise of course. I don't know if you happen to have a keyway on the output shaft, to use for a position reference to simplify locating TDC.
With only one piston ring, if it turns out to be fairly worn, it may not give enough compression to run. However, let's wait for the test data.
