| Also known as | 370L |
| Diagram | Fig. 18 — HEADLAMP, SPEEDOMETER, TACHOMETER · ref 15 |
| Subsystem | electrical |
| Listed in parts books | 1971–1974 |
Main bulb (45; 35W) (99- 1214)
Lucas 370 main headlamp bulb, 45/35W dual-filament, superseded by 370L.
This is the main headlamp bulb, Lucas part number 370, later superseded by 370L. It's a dual-filament 12-volt unit that gives you both the high beam and low beam out of one bulb, seated in the headlamp shell behind the lens and reflector.
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Our catalog shows it appearing across a wide range of headlamp, speedometer, and tachometer figures, and it turns up in the battery and TR6C headlamp listings too, so this is the bulb that most of the British bikes of the era used up front. If your parts book still lists the older 370 designation, know that 370L is the same physical bulb under the newer number.
When you're replacing one of these, check the bulb holder and the pre-focus base seat carefully going back in, since a bulb that isn't indexed right in the reflector will throw the beam pattern off even if the bulb itself is fine.
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