I don't think those old bikes needed a battery. I'm pretty sure the magneto did all the electrical power work. That thing looks pretty rough. Check the on off switch see if it's functioning and I don't mean just flip it back and forth open up the housing and check it . If it is the temporary push button type of kill switch...bypass it temporarily and see if you get a spark. Trace the wiring back from the plug all the way back and check connections and repair as you go if necessary. make sure it's not grounding out anywhere or filled with dirt/rust/corrosion.
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