Have just purchased a. 1971 BSA Goldstar SS 500 This has a unusual electrical system. Thought this had capacitor ignition. Could this be the ET ignition. Has 12V + ground, battery, rectifier, zener diode. The coil is not normal 12V (sealed in rubber compound) The bike has no spark. Anyone know how to test this coil? I am very much afraid this has the dreaded ET system. Didn’t think they had a battery. Any help would be greatly appreciated. Thank You