The optical pick-up is a crank position sensor. It "reads" the tiny slots in the thin stainless plate located under the distributor rotor button. That info is sent to the ECU which triggers the power relay(located on the flat bracket beside the distributor) to energize the ignition coil.I hope this is correct , I'm open to correction if I'm wrong.

When acquired my Raider it had been setting for 6 yrs. After draining the gas & replacing it w/ fresh ;it would turn over hit once or twice & that was as far as it would go. I did a complete tune-up, same thing. Replaced the optical P/U ($109) - it ran..I believe there are troubleshooting instructions in the down-loadable manuals. I'll try to find some page #'s & get back to you.