Before spending the big bucks on a Hall sensor, check your circuitry - if the starter relay has a diode feeding a mystery loop through the tach or ignition circuit, replace it for about $18 from the dealer.
I had a mystery problem with my R80 ST after rebuilding the tranny where it would just shut down and not restart for several tries of the start button. After repacing the starter relay (which was not the original one) all problems were cured. Notice the fact that it it would shut down - not a normal starter relay problem - but related to the extra circuit apparently.
Merritt Island, FL
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