I agree that what we need to see is fuel, compression and spark. At the moment you've reported electrical activity in the plug lead at slow rotation of the engine, but you haven't reported spark. I suggest you make an actual spark test, with a device like this:
[Linked Image]

Connect the plug lead to the top of the spark plug, and attach the clamp to a metal part of the engine. Pull the starter in the normal way.

Begin by using the actual spark plug from the engine, with its normal gap. If you get a steady series of blue sparks across the gap, things are not looking infinitely bad, but it may still not run well. The second step is to fit a comparison spark plug (usually an old one formerly used in a car), with the gap set to 0.060". This slightly larger gap is to simulate the higher air pressure in the cylinder at full compression. If it will spark the original plug at standard gap, the engine will probably start. If it will spark the comparison plug at 0.060", it will probably run more or less decently.

You can do the test without making the tester, just by holding the metal body of the plug against the engine while you pull the starter. It isn't as convenient, but you can get the job done that way if you play with engines so rarely that it isn't worth setting up to do it conveniently.