Some more "basics"
You need compression, spark, and fuel
1...Compression--enough of it--have you checked compression? What is the miles on this engine and what condition is it in? You might consider checking the spark. Have the valves been adjusted? Is it possible they are sticky/ gummy after sitting? ALSO IT IS possible that you have enough fuel down in there to "wash down" the cylinder walls and decrease compression. Maybe squirt a little oil in each hole, crank it a bit to distribute, and re-check compression
2...SPARK---Hot enough spark and at at the right TIME. HOW did you check spark? If you are checking from the stock radio suppressed coil wire, this gives you a "poor picture." Use a test gap, connected to the coil with a SOLID core wire and you should get at least 3/8 and more likely 1/2" of hot blue spark.
Points/ condenser--If the spark is weak, maybe the points are old, coroded, burned. You MUST have a good condenser, and they can go bad. There is no easy way to test condensers, regardless of internet "wisdom." You need a special high-voltage leakage tester,--something you cannot duplicate
If you have left the key "on" while you are trying to start, you may have burned/ damaged the points
Condition of cap, wires, etch--check for dirt, debri, carbon, how old are the wires? Check the wires for individual continuity. Resistor/ radio wires "rule of thumb" is "no more" than 1000 ohms per foot of wire, good ones almost always less
3...Fuel........Are you using fresh fuel? Make sure. Regardless of condition of the tank/ pump/ carb, about a teaspoon of good fresh fuel down the carb through should result in the engine firing for a short time.
