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Lucas Tail Lamp Adapter Triumph Thruxton Bonneville Scrambler

Updated: Aug 15, 2023

Fitting a Lucas Tail Lamp on a Triumph Twin is not as easy as you would think. Installing it in the most desirable position offers challenges, as the large hole the wires feed through is in exactly the same position as the screw holes that mount the housing.  So you have to rethink, and raise or lower the housing. Also avoiding the large depression in the fender that was made for the stock bubble lamp.   Now you have found the perfect, compromised, make do location three holes will need to be drilled.

Then you will find the lamp sits at, err well.....  not quite the angle you had in mind.  The hideous muffin top gasket you are expected to use hiding the poor fit will also be needed unfortunately.                                  A lot of time and effort for a disappointing result.   That is why I decided to make a handsome bolt on, no drilling, adapter plate that fits stock fender holes and keeps the lamp rubber mounted as Triumph originally designed.  The lamp, housing, adapter plate, neoprene gasket is sold as a kit with all necessary stainless hardware.


Lucas Tail Lamp History Lesson     Housing in picture on left has a Lucas 525 lamp mounted. These were produced from 1953-55.  The kit is supplied with the Lucas 564 lamp which was introduced in 1955. This lamp has the Reflex reflector molded into the lens. Both lamps fit the same housing and have clear lens underside to illuminate license plate. You will find either of the two give better light than stock light.

FITTING.  Once the stock lamp is removed the 3 steel ferrules that fit in the rubber grommets will need to be inserted with the flange on top side of fender.  Lamp and adapter can be fitted with supplied neoprene gasket directly on fender and tightened with the 3 stainless screws, washers on the underside and original nuts.   Fits perfect !

Kit is supplied with vibration/water proof sheathed wire connections. The ground wire of the harness is split into 3 wires as shown on (schematic diagram)


Triumph Bonneville Thruxton Scrambler Tail light/Turn signal harness schematic diagram

Harness wire color                Lamp wire Color                          --Connects to-- Red  (running light)                Black Blue  (brake)                         Red Black  (ground)                     Brown Orange                                  + Turn signal Left Brown                                   + Turn signal Right

Turn Signals

BLACK.........POSITIVE +

BLACK/WHITE .......NEGATIVE -

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James
James
Feb 06, 2019

An alternative is this housing, allowing use of stock signals or supply your own.

https://www.maundspeed.com/product-page/525-fender-mount-lamp-housing-bonnie-thrux-scram?categoryId=75896673-91eb-496b-a34e-a68da8cf55ef

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James
James
Feb 06, 2019

Hi Phil, I am sure, as is, the signal spacing is not sufficient. If you go to this page https://www.maundspeed.com/product-page/lucas-tail-light-adapter-kit-bonnie-thrux-scram?categoryId=75896673-91eb-496b-a34e-a68da8cf55ef

look at sixth picture with German license plate, you can see the customer supplied his own signals with longer stems. I believe they are Honda 400/4 or Cb type.

I can supply kit without signals if preferred.

All shipping prices are given if you add to cart> go to checkout> enter country and territory. Please email me from contact page of my site for custom orders. Hope this helps .

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phildixon94
Feb 06, 2019

Hi there..love the look of these tail lights etc was just curious of the distance between indicators due to laws in my part of Australia..also postage cost to Queensland Aus

Cheers Phil

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Maundspeed Triumph Thruxton Scrambler Bonneville parts Los Angeles Ca
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