Lucas E3L Dynamo
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.
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.
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.