For Magdyno straps click here; for battery carriers click here; for magneto and dynamo sprockets click here.

Lucas supplied the electrical equipment for all models except the C10L and most Bantams. Magdynos were used on the B and M groups apart from the 1958-60 B group, which were fitted with alternators; the C group used a dynamo and distributor until 1953 and then an alternator, while the A group used a separate magneto and dynamo.

Lucas used a comprehensive numbering system that can be a bit unwieldy at first but it is worth getting to grips with. Each type of item (e.g. dynamo) that they produced had a model designation (e.g. E3LM), the 1936-57 Lucas catalogue lists 18 models of dynamos. The model designation can be decoded, for our example E=Eccentrically mounted armature; 3=3” diameter; L=Long body or yoke; M=Magneto mounted. For most models there are several variants, each of which has their own ordering number even though the difference might be only one part, this results in 72 different dynamos from those 18 models. The model designation and the ordering number are invariably stamped onto a major part of the component as well as the month and year of manufacture. Needless to say this information is very useful to restorers.

The direction of rotation of a component is taken to be as viewed from the drive end. E3 in this list means all E3 dynamos’ i.e. E3HM, E3LM etc similarly E3L means E3L and E3LM and so on. The table below can be used to see if you have the correct item on your bike and is necessary as the applications in the listing below is mainly by the type of equipment fitted rather than by the BSA model.


Dynamo or

Magneto or

1947-49 A group E3H K2F
1950-62 A group E3L K2F
1936-49 B and M group E3HM MO1
1950-57 B and M group E3LM MO1L
1958-60 B31/3 RM15 18D1
1958-62 B32/4 and M20/21 E3LM MO1L
1939-48 C10/11 E3H DKX1A
1949-53 C10/11 E3L DKX1A
1954-55 C11 RM13
1956-58 C12 RM13/15

Magneto and Dynamo Repairs

We repair your old unit rather than exchanging it for a reconditioned item. A repair usually takes 2-3 weeks but does depend on the workload. The cost varies depending upon the parts required but the armature will almost always need replacing. We strip and clean the parts before they are blasted, painted or plated. The unit is then assembled with any new parts required and is fully tested. They are of course covered by our flexible guarantee. Please tell us whether you are using negative or positive earth, 6 or 12 volts and the machine details.


Show sidebar