Magneto Not Providing Spark

[julian.murphy]

M01 magneto as fitted to 1957 NH.

This mag ran on the bike for 20 years without a hitch.

The bike has been dry stored for 12 years (last tax disc 12/2000). When stored away, the mag was functioning fine, fat juicy spark.

Now I'm just recommissioning to use again, but the mag is not functioning.

What has happened?

Has it lost magnetism from not being used?

Any other clues?

What to do:

1. Send this magneto to a specialist for overhaul.

2. Buy/fit electronic ignition kit. Needs 250 Ma at 12v. I have 12 v 7 A on the bike (12v converted a number of years ago)

Anybody got anything good/bad about electronic ign units?

Looks to replace complete points assembly but retaining the rotating spindle and adv/retard mechanism.

[nevhunter]

How damp was the place where it was stored? Moisture is the enemy of armatures in magnetos
The first thing to check is the points. I would suggest you remove the points assembly and clean the faces of the points carefully and check that the little fibre push rod that runs around the face cam hasn't jammed in the diemetal body of the assembly. Replace, adjust points to about '015" and give it a kick. Magnetos left on bikes don't lose magnetism totally. They fare much worse when left dismantled without an armature in the case to act as a "keeper"..Nev

[julian.murphy]

Thanks Nev.

Well the storage was in a 'vacu-bag' with dessicant (changed infrequently). Must have been pretty dry as the aluminium is not corroded and still bright, the chromework still shiney, in fact probably all as good as the day I stored it away.

Will have a look at the points and plunger later.

[nevhunter]

You've certainly done the right thing there with the bag. The later post war models have pretty good windings. when you get back into the 20's I usually recommend rewinding them as rarely do they run for more than a few days before the shellac runs out of the armature, and locks the whole thing up. Nev

[julian.murphy]

Removed points and cleaned up both faces on a fine stone, and degreased.

The plunger is operating correctly.

Removed HT lead and cleaned bottom end to ensure good contact into mag.

Fitted another plug cap also.

Still no spark.

Arrgh!

[robin.parker]

It may be worth removing the HT pickup and carefully cleaning the Slipring in the Mag, by poking a clean rag in the hole and rotating the mag, slowly! and being careful not to damage the said slipring.

[Simon.Gardiner]

Looks like this little beastie has decided to be difficult.
-while the HT pickup is off clean/degrease it thoroughly
-make sure the HT pickup brush can move freely and see if you can work out if there's enough 'push' in the spring to get it in contact with the slip ring
-do the same with the earth brush

If still no spark, make sure plug lead has just plain copper wire core, unscrew plug cap and see if you can get any kind of spark from the end of the lead to a good earth. Be prepared to check with a very small gap, the plug gap for a mag ignition is smaller than is normally used these days (if you're unlucky 20 thou=no start, 15 thou=no problem!)

And the very best of luck!