Aloha,

Spent last weekend visiting my M21 in my garage in Gothenburg (currently live in Stockholm). I previously had a good spark on the magneto form just turning it over by hand. But somehow when I have mounted the magneto on the engine the spark has gone missing! Mounted it some time ago but only this last weekend did I get to check the spark by kicking it over. I of course have tried adjusting the points gap, and looked for obvious connection errors. I have a good "beep"-connection between the spark plug lead and the brush for instance.

Any clues, ideas, tips as to what might be going on here?

Could it be that the points have developed a light film of corrosion? Have you tried just cleaning them with a little bit of sandpaper
Dave

email (option): davmax@ntlworld.com

Thanx!

No I haven't, I'll give that a go next time I get around to work on the bike. Which will be 'round x-mas.

If Dave's advise doesnt make a difference, you could also take off the HT lead and clean the brush and more important, the ring inside.
That sometimes works and is easy to do.
Also check the earth brush.

Let us know how you get on, for others to be of help.

Make sure that the bolt that holds the points assembly to the armature is done up.

Ensure you have continuity from magneto body to spark plug body. Seriously.

Thank you all for good input! Unfortunately I have addressed all of them already. Apart from checking the earth brush. That will be next.
Will post follow ups as asked for. Glad if I can help since I have found lots of good info following this forum.

/simon

What is the history of the magneto ? If it hasn't been rebuilt, I'd be inclined to assume that the previous spark was an optical illusion, the reflection of the aurora borealis (you can see it from Sweden, can't you)...and rebuild the blasted mag anyway.

Magnetos are sentient beings and they like to play games. There are no shortcuts and if procedures are not followed then problems will inevitably follow.

If it has been rebuilt, take it back for testing.

The magneto has gotten new bearings brushes, points and some other small details.
The spark however was not just an optical illusion. When I had first assembled it I hooked up a wire/spark plug lead (or what ever it is called) and was standing holding the magneto while sort of looking around the workplace trying to figure out a good way to hook i up to a drilling machine in order to test it. As I was standing there I was kinda turning the magneto over in a slightly distracted manner and ZAPP! I got an electric chock in my fingers from the wire. When I the held the wire close to the magneto and turned it over I could also actually see a spark.
So more than an optical illusion.

/s

Ok,

So if I am to take the magneto apart looking for issues, what are the main things to do? Kinda new to magnetos since my previous bikes has all had batteries, points, coils, primary ignition coils, Boyer and what not -but never a magneto.

A link to some website or something will be fine, I don't expect for someone to write me a complete manual on magneto restoration and troubleshooting.

/s