6 - 12 Volt Conversions

First Question... Why do you want 12 volt electrics?

Possible Answers... Brighter lights, extra electrical equipment, alternator installation.

Brighter lights, if you don't ride at night (like 99% of classic bike riders) you don't need brighter lights. But if you do this can also be accomplished by fitting a Halogen headlight bulb that are available with the old style connectors. The are rated at similar Wattage's to the original equipment so will draw no more power but will provide much brighter lighting.

Extra electrical equipment equipment... Your having a laugh, it's a 50 year old classic after all! If you must do this then go for the alternator update.

Alternator installation, if your going to the expense of an alternator conversion then I see no reason not to go the whole hog and fit 12 volt electrics... see below for details.   


An Alternator conversion which keeps the original appearance of the bike is available from Hawker Electrical (see Here) and Alec Jay Motorcycles, Woking, England. (See Links page for full contact details). The MC45 series of dynamos are now very hard to get hold of and also have poor output. This conversion is available as either 6 or 12V although I see no reason to stick with 6V electrics, and will greatly improve charging and lighting performance ect. Don't forget to get your Lucas Altette horn upgraded for 12V, because although the 6V version will work for a while. it will eventually burn out... Altette horns are very expensive. They can be upgraded although you can't get the parts for DIY, but another alternative is to leave the 6V one on for show and to fit another modern horn out of sight.

Coils, bulbs and battery ect... will also need to be replaced for a 12V conversion.

Halogen Headlight Bulbs

You can now buy Halogen headlight bulbs that fit the old style headlight bulb connectors, they are available in either 6V or 12V varieties and cost about 5 UKP ($7 USD) and are a massive improvement for a very reasonable outlay.

Lucas Altette Horn

As previously mentioned it is important to get your Lucas Altette horn upgraded or replaced if you convert your motorcycle to 12V, because although some sources will tell you that the horn is OK because its only 'on' momentarily, it WILL eventually burn out. I do not know of any DIY source of Lucas Altette Horn internals, however 'Taff the horn' (don't laugh) in Wales is a Wizard with these items and has a business based around repairing and upgrading horns. He has customers worldwide and currently has a 3 month waiting list. If you can't wait that long it is possible to get a reproduction copy of a Lucas altette from Europe for about 85 Sterling. A lot of people sneer at these although they look and perform well but are not exact copies and parts are not interchangeable. Another option is to get a 12V car or lorry Altette from an autojumble, these quite often don't have the chrome ring and domed nuts of the motorcycle type so can be bought a lot cheaper especially if it has a rusty appearance. You can then remove the outside ring and nuts, wire brush it and spray it black, and then use you the chrome parts from your original 6V version (they will fit) to make it look pretty again. 'Taff the horn' contact details can be found on the Links page.

Also see: SUNBEAM: Technical: Electrical: Rebuilding Altette Horns

Dynamo to Alternator Conversion - Supplied by Alec  Jay Motorcycles, Woking, Surrey, UK.

This conversion looks VERY similar to the original dynamo and therefore keeps the stock appearance of the original bike, I will however get some photographs of a finished bike in the near future. Alec Jay Motorcycles state 'The fitted kit is very similar in size and shape to the original Lucas (MC45 series) Dynamo and will add a new lease of life to these popular bikes. Your wiring loom, ignition switch, distributer and points, ect... need to be in good condition - If in doubt, replace!!'.

    The kit consists of...
    1/. Machined Alternator Housing Complete With Mounting Studs & End Cover.
    2/. Rotor Adaptor and Woodruff Key.
    3/. Modified Left Hand Dynamo Fix Bolt (Please Send Your Bolt).
    4/. Lucas 12 Volt Alternator Set.
    5/. Lucas Positive Earth Diode and Connecting Wire.
    6/. Diode Heat Sink & Bracket.
    7/. Solid State Rectifier and Bracket.
    You will also need...
    1/. 12 Volt Ignition Coil.
    2/. 12 Volt Battery (12N9-3B, CB9-3B ect..)
    3/. 12 Volt Bulbs (all)
    4/. 12 Volt Horn (See Altette Horn Above)
    Also recommended...
    1/. Lucas 12-12 Ammeter
    2/. Wipac Quadoptic (or other) Headlight Unit - 55/60 Watt Halogen Bulb.

The kit does not come cheap but could be your only option as working MC45L dynamo's are hard to get, and you will have the benefit of 12V electrics, solid state rectification and greatly up-rated generator output.

The basic kit costs 327.66 +VAT (385) but over-sea's buyers should be able to get away without paying the VAT, you will however pay for international carriage which will probably mean that UK and international buyers end up paying the same amount.

Converting to Electronic Ignition

Although there are many companies out there producing electronic ignition systems (Boyer, Rita, Newtronics ect), very few of them make a system for the shaft drive Sunbeam. It may be possible to get an expert such as Kirby Rowbotham (Net:, Email:, Tel. +44 (0) 1889 584758 ) or one of the American agents listed on his website to convert a Boyer type electronic ignition unit into your standard distributor.

If your aim is just to ease starting and provide reliable timing then you may wish to consider a modification sent to us by Juergen Schuepbach in Switzerland which uses the standard distributor as a clocking device at low voltage for an electronic ignition module that provides the signal to the coil. Although this is a 'Points Assisted' system there is no condensor to fail and the points are only being used as a switch at low current which means there is very little or no arcing and therefore little degradation to the contact point surface, ever!.

Juergen can also provide kits or fully assembled Electronic Ignition modules. Click Here For Further Details 

Front Wheel / Brake

The S8 and S7 Deluxe front brake can be greatly improved by using a BSA Goldstar front hub and lacing it to a standard Sunbeam front rim. The Sunbeam was always criticised for its stopping power and this is the brake that BSA should have fitted as soon as the Sunbeam received BSA forks in 1949.


It is often stated that this modification can be performed with no other changes... this is NOT true, (Bitter Experience). BSA 8" hubs may differ model to model and will require that the Sunbeam fork fitting and brake pivot are modified accordingly... of course if your a competent engineer with access to material and equipment then you may be ok... otherwise buy a new standard hub from Stewarts which a guaranteed to be perfectly circular and use good quality brake linings and your breaks will be better than new.


Amal Concentric

A Stewart Engineering supplied Amal Concentric '624' Carburettor can be used in place of the original Amal 'Standard' 276 with remote float chamber 3A. Although fitment is relatively straight forward you will have to modify the air filter and cover fitting and also fit a choke lever and cable somewhere on your bike. The Stewart carburettor is heavily modified and a standard Amal 624 concentric CANNOT be used or modified for use. Ring Stewart Engineering for further details (See Links page).

Amal 276 carburettor's are available new, although the 3A remote float chamber isn't, so you'll have to reuse your old one if your don't want to use a concentric and need a new carburettor. (I may have spares... e-mail me for details). Although the only new models available are right hand version which make carb adjustment and setup very awkward as the float chamber is in the way. The original Sunbeam 276 carburettor was a Left hand version.

Also see: SUNBEAM: Technical: Carburettors.