Service Bulletin: Lucas #446 Headlight Bulb Failures
Triumph Service Bulletin #16 5-13-1966
"Have you ever thought that vibration could be the reason why your headlight bulb failed?"
Dated May 13, 1966, this Triumph service bulletin goes straight to the point on failing Lucas #446 headlight bulbs.There is usually a reason why things fail, some under different circumstances. In regards to headlight bulbs it could be quality, an electrical short, bad diode, overcharging, and other variables. Have you ever thought that vibration could be the main reason why your headlight bulb failed?
Vibration can be destructive especially to parts that are not properly isolated. British motorcycles are notorious for having vibration issues. Vibrations can cause ammeters to fail, fenders and brackets to crack, bulb filaments to burn out and hardware to go M.I.A. Its imperative to confront these problems.
The fix is to try an isolate the headlight shell from the fork brackets by using rubber grommets on both sides of the headlight bucket. For those riding enduro or off-road it would be a wise modification to rubber isolate the headlight shell. I personally like to keep back-up bulbs with me at all times. Not just headlight bulbs but also tail light bulbs and turn signal bulbs. Most auto-parts stores do not have bulbs that will fit a vintage British motorcycle so its wise to have back-ups handy.