Sounds like timing is not your problem, like mech says pretty much if there opening and closing you should have spark.
Make sure the points contacts are clean, also check all your connections.
Sometimes ive seen someone has hooked up the point wrong, ie bolt insulators put on wrong grounding out the points connection.
How are you checking the spark ? Do you have the plug cap off the end of the leed ?
When i was sixteen i pulled the motor out of mine, and upon assembly pinched the magneto wires between the motor and frame ? Hey its possible.
If your getting spark there is life, however weak. Gotto be something trivial !
Also try unplugging the ignition switch
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