| Diagram | Fig. 18 — HEADLAMP, SPEEDOMETER, TACHOMETER · ref 12 |
| Subsystem | electrical |
| Listed in parts books | 1971–1974 |
Light unit (99-1212)
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This is the light unit that goes behind the rim on a Lucas 5 3/4 inch headlamp bucket, catalog number 54525272, also cross-referenced as 99-1212. It's the reflector, lens, and bulb holder assembly as a whole, not just the glass or just the reflector separately, so when this fails or corrodes you're replacing the works in one shot rather than trying to source the reflector and lens as separate pieces.
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In the parts books this one shows up under headlamp and instrument figures, including a listing specific to the TR6C battery and headlamp setup, and it appears across catalog entries running 1971 to 1974. Some of the figure titles it's tied to also cover the Fastback, Fastback L.R., Roadster, Interpol, and Interstate variants, which tells you this light unit saw duty beyond just one model line.
If you're rebuilding a headlamp shell and the old reflector is pitted, clouded, or the lens has cracked, this is the part number to hand across the counter. Bring the old unit or your bike's model info if you're not sure this is the right one for your setup, since the fitment on these can vary by model and year and the catalog listing alone doesn't spell out every application.
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