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Did you check the "BATT" wire for POWER with the key in the run position, and was it 12 volts?
If it was, did you again try it during cranking mode? Did it drop to zero?
If that happens you have a problem between the run and start set of contacts on the switch, (usually a jumper on the plug) You Can run a secondary ignition from the "R" terminal on the starter and parallel it in at the "BATT" wire to support power during crank as an easy fix for this.
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