Lucas Dynamo


For Sale Lucas MO1L Magneto Parts.


Service Sheets for BSA MotorCyles and Lucas Electrical  for Sale.


E3HM-LC Dynamo Powertest Video ( Thanks to Marinus in Indonesia )

Lucas E3L Dynamo ( From www.audioworld.net )


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From a period when "English Workmanship" was something nice. The bike has retained the 6v system, as I feel this is a "part" of the machine. But I can understand why 12v conversions are popular. The work and adjustments to keep the Lucas mechanical regulator happy can put anyone off, but it's very rewarding when it works as it did 50 years ago. The dynamo has been trough an overhaul involving among other things a repair of faulty windings at the commutator. Some wires seemed to have been torn loose by centrifugal force. A careful soldering job and then repacking all exposed wires with epoxy glue solved the problem. It was still not possible to drive too much with full lights without draining the battery. To counteract this the 3w pilot light was changed for a 10w halogen torchlight lamp. This gives as much light as the 30W mainlight, but has made it possible to have bright headlights and a full battery. Osram makes a 10W lamp for the  Ba9s socket. The 10w lamp needed a 0,5 ohm resistor in series. I haven't changed a lamp or had to charge the battery since winter 98.


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E3L brushes and commutator.

To check voltage output while mounted on engine connect a lamp between the shorted two outputs and the frame and start the bike. Use a 12v lamp due to the unregulated output. The lamp should light up brightly right over idling speed and give more or less light according to engine speed. This denotes that the dynamo is OK, and if you have any electrical problems look elsewhere. By the way, adding a fuse (8 to 10A) to the battery cable is a good idea. This can prevent  damage if cables short etc, and it also provides a quick way to disconnect power when working on the bike's electrics.

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Dynamo drive

When the rivets are loose or gone, one can make a durable repair  with screws & bolts. I used recessed screw heads & loctite (green) + locking washers on the nuts, in addition I used a hammer & punch to really lock the nuts for good. Or one can opt for a belt drive system, which should eliminate rivet & chain tension problems.