1936 Model 50 - no sparks

Unfortunately the capacitor in your magneto could have failed, or the windings. You will probably have to take the magdyno off the bike and have it repaired by a specialist.

Colin.

Richard,

I own a 1938 model 50 and had ignition probs. You can try putting a meter across the points but it will need to be quite a good one as the windings have a low resistance to start with so appear to be nearly short even when the circuit breaker is open.

You could check that the HT lead is seated properly and if you remove the magneto you should be able to get a spark by spinning the magneto directly by hand (it will only work the correct direction)

The other check you could do is to remove the rotor. If it has a dark brown / reddish lacquer this will be original and probably need a rewind if you want reliable running when its warm...but you may be lucky. A rewind cost me about £200 last year.

Gary

Hi Richard,

The Lucas condensers had a very limited life compared to some other brands, without testing I can assure you your capacitor is either shot, or will be very soon. There are some tests that can be done in the home shop to test the armature once it is removed from the mag. If the windings are soft, or squishy, time for a rewind. The high tension lead should read about 4,500-6,000 ohms, and the lt side should be about .6 ohms (thats a little more than 1/2 an ohm). I like to heat the armature to 80 degrees Centigrade & test again to see if there are any insulation issues, but be sure the missus is gone when you "borrow" the oven

There is a test for the slip ring & pick-ups also. You might enjoy looking at the Brightspark website for more info & be sure to check out the library to see the Lucas sheets on your mag/dyno.

There is also the issue of having the magnet recharged & the bearings checked out while doing the other work.

Please dont hesitate to fire any questions my way, always happy to help where I can.

My email is sbrolund@yahoo.com

All the best,

Skip Brolund

?

I wish I had not oven tested my mag. That is what wrecked it. You need reliable temperature control and I did not. If you approach 100 deg C the shellac will melt and clog it up entirely. Mine did. Brightspark fixed it (at least I hope so - not re-assembled yet... fingers crossed...). So take great care.

Condensers fitted to Lucas mags absorb water and even the NOS ones fail miserably. I'm not sure that the very early ones are any better or worse than the later ones, but if its still an original pre-war winding and condenser its well past its best and should probably be looked at. Whenever we get a mag in, if its an original Lucas condenser, or original shellac insulated winding, we don't even test them. Take a look at www.themagnetoguys.co.uk.

It's my dads business and as I am away at university at the moment he is working on his own. If you want him to look at it I think he currently has a back log of about 3-4 months (over 70 sat in the workshop waiting to be done). So it wont be quick and you might want to go elsewhere. There is however quite a lot of info on the website and it will give you some ideas of what to ask anyone you ring up about doing the job as some people do cut corners and not do as good a job.

Hi Richard, Check the points gap and give thema quick clean with fine emery paper. You need to check the brushes are ok, oneinside the pick-up, and the earth one under the brass screw. make sure the HTlead isn't corroded and tape or hold the HT lead on to the mag body with thecopper ends about 1/2mm away. spin the mag the right way and if the mags ok youshould get a spark.

Your mag (if it's anoriginal one) will have a mica condenser fitted. This is better than the laterpaper insulated condensers, as the paper would fail. The mica condenser isbetter than a modern replacement.

I stripped my 1940mag and it had a mica condenser, that is about the change over year to paper soI was lucky. I took the armature to a very helpful man called John, justoutside Stroud (UK) and he tested the windings which were ok. It is the lacquerthat melts, goes soft and causes the windings to short. Mine was a bit soft butstill ok. He said even if he rewound the armature he wouldn't change a mica condenser,as they do not fail and the life span of a new one isn't good. A rewind of thearmature will cost about £100-£120 then you can assemble the mag yourself.Remember to take out the pick-up before knocking out the armature or you'llcrack the bakelite pick-up ring.

Give John at Magneto repairs a ring, he's very helpful.

Magneto RepairsMerlins MillToadsmoor RoadBrimscombeSTROUD, Glos.GL5 2UG

Telephone: 01453-886849 (office hours 10 to 12.30, then 2 till 5, Monday to Friday, callers by appointment only please)