Remember all systems can be broken down to the basic elements and while running well is the goal, the irreducible components define if it will run at all.
Take a compressor and air hose, spray through your carb and make sure that it is sucking fuel into the mix. This will sometimes expose a clogged passage in the carb.
alternate- if it does not start with starter fluid you may be spraying toooo much into system (its not a car so you dont need much)
Its not good enough to take out the plug and see if it sparks when turned over, because it tells you nothing about the normal opperation. You may have carbon tracking some other place. Wash plug boots and point area with Isopropyl to remove all oil and carbon.
ALSO: make sure that your points are VERY clean (some 600 grit sandpaper should clean them fine)
You can do a quick check of timing without the timing light as follows. Use a thin dowel or something of the sort into plug hole. Mark at TDC and BDC. Rotate the engine by hand in direction of rotation and mark location of point release (use a mutli meter not your eyes)
If it blows it goes. You dont need good compression for it to run, only for it to run well. You should not have an issue here.
If you have valves in your system you may need to use some penetrating oil or something to make sure that they are not stuck. Others here are likely to know more than I since I dont do 2-C valves.
If gas is REAL old the vaporization may be a factor but not likely.
Your system may have a short from ignition to ground (how they usually workit in key'd system), make sure that there is nothing grounding out the electrical system on the ignition side.