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Topics - oldgoat

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British Bikes / Wiring 1967 BSA Starfire
« on: June 29, 2021, 02:09:35 PM »
Ive picked up a junkyard 67 BSA Starfire 250, engine/frame number C1429. It was an absolute mess the PO had installed extended forks, V-line handlebars, now-rusted chrome do-dads. Ive managed to replace all that crap with stock items, and now I want to get her running. The original wiring harness had been modified and was pretty much rotted away. I bought a replacement, but there are some discrepancies between the wiring diagrams in my Haynes manual (BSA Unit Singles 1958-1972 Owners Workshop Manual, 1980). Does anybody on the forum have familiarity with the wiring on this beast? Ive managed to have ridden for 52 years without ever having to do any motorcycle wiring, so I am a real novice. Obviously with the harness taped up the way that it is, I cannot follow individual wires end to end, so Im working off wire colors and their positioning on the harness.

So, the first question regards the wiring to the ignition switch (IS). The switch has 3 terminals. According to the manual, the connections should be W from the coil, NW from the Zener diode, and NW from the rectifier. But the IS portion of the harness has two push-on clips: one clip has 2 W wires. I assume this is from the negative terminal of the coil (which has a W wire), but why are there two W wires? The other clip has two NW wires. Are these from the Zener diode and the rectifier? If so, why are they wired together? How should they be positioned on the switch one at each end, leaving the middle terminal open (or covered)?

The rectifier: It has 4 fins. The outermost one (furthest from the frame) is labeled ("Stud +"), so I assume the red wire from the harness (which has an eye terminal) is bolted there. The other three wires from the harness are NW (I assume from the ignition switch), GW and GY (both apparently from the alternator). Which order should these 3 wires be positioned on the fins?

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