| Diagram | Fig. 17 — NACELLE HEADLAMP AND SWITCHES · ref 19 |
| Subsystem | electrical |
| Listed in parts books | 1964–1966 |
Bulb (50/40 W. L. H. - dipping Prefocus)
A 50/40 watt dual-filament prefocus headlamp bulb for the nacelle headlamp assembly, later superseded by part 446L.
This is the headlamp bulb Lucas listed as a 50/40 watt prefocus unit, the kind fitted in the nacelle headlamp assembly on the bikes it shows up for in our catalog records from 1964 to 1966. It's a dual-filament bulb, meaning one filament handles the low beam and one handles the high, and it seats into the reflector using a prefocus base so the beam pattern lines up correctly without adjustment at the bulb itself.
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In our records this part carries the number 414 but was later superseded by 446L, so if your parts book or an old invoice shows either number, they point to the same physical bulb. It also turns up under the JRC 18-025 designation in some listings.
If you're pulling the nacelle apart to replace this, check the socket and reflector for corrosion while you're in there — it's a good time to look at the whole headlamp assembly rather than just swap the bulb and button it back up.
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