Forum

[Martin]

On early 500 twins, the Lucas generator
and coil ignition distributor is one unit.

Replaced brushes, and new bearings, field
coils seem OK, but did not have buzzer to
throughly check the armature.

Anyway, minimal output with 1000rpm drill
attached, either .375V, or 3.75V. Took it
a starter/alternator repair shop with the
zeroxed spec. sheets, but they had never
seen such archaic artifacts, and merely
annouced it didn't 'produce'..GEEZ,I know
that already..

Someone suggested just ride it without
any current, and am sure to have done that
long ago with defunct Magdynos. So, aside
from discreet use of the stop light, how
long can get from a fully charged medium
'bike battery with just coil ignition...
or what is the actual amperage drain?

Am overseas, and already know this unit
is only fitted to the Square Four. Weight
is too heavy for posting, so a summer time
comprimise.

Thank you!

[Norm]

Gordon,
Don't waste your time with Iron Horse, I waited 8 weeks trying to get an answer from him and I gave up and am now waiting on my new inner primary to be finished welding and then I will be running a crank alternator using Bullet parts and Bullet outer primary. Hopefully in a week or so it should be up and running. I have already wired it neg earth to suit the Bullet rec/reg unit so soon we will have lights,decent lights and a charged battery.

[Les H]

Hi Gordon. I'm not sure if I've missed anything after reading Norm's reply but if you are saying the dynamo on the mag dynamo has stopped charging then I was going to tell you the Lucas dynamo is usually the E3L type. These dynamos can be easily be dismantled and repaired, even a brand new armature is quite cheap and lots on Ebay (last time I looked) As a quick check to rule out the regulator is to wire together the A and F outputs on the rear of the dynamo then measure the voltage created from this junction and earth (frame) hard wiring the A&F terminals maximises the output. If you are willing to check this you will be off to a good start in finding the problem. I won't describe any more checks at this stage. I'll leave it to you to bother if you want. BTW, The coil draws around 3 amps so you are not going to get more than an hour and a half running from a 5 A/H battery. Oh yes normal lead acid batteries are not designed to be constantly discharged right down and then fully charged again as the plates begin to breakdown. If you are going to continue using batteries you'd be better off using Ni-cads or NiMH type. better to mend the dynamo or regulator (Solid state available cheaply too) it's quite easy.

[Les H]

BTW when I said magdynamo, I meant combined dynamo and dist unit (not seen many of those!) ....don't know what year your bike is, but you say you have a dynamo (generator)

[Martin]

Sorry, confused the issue by mentioning
Magdynos from machines lomg ago. The 1950
500 twin has the C35S/O Dynamo, and the
DKK B2A vertical distrubtor used on '49/'52
twins, and only other machine is the Ariel
square four according to the Lucas parts
book. The armature is quite long, and has
helical teeth for the perpendicular dist.
Anyway, have all the diagnosis info, and
just need the armature 'buzzed' to see if
that's faulty which would be a bummer. Am
grateful for Les clarifying the coils 3amp
per hour discharge which would drain a 5amp
battery fast and cripple a plate battery.

Thanxs, I need a stiff drink!

[simon]

The residual magnetism in the field magnet can get so low that it will not self excite with the old Lucas generators. Usually it will come up after a while but motoring it can bring it back to life. By motoring I mean connecting it to the battery so that it runs like a motor which it will do if the armature is in good order. If it won't motor it might be time for a rewind. Generally though they work extremely well.