The Magneto Maintenance Page


Updated: Sunday 11th March 2007

Out with the box of pre prepared parts and off with the temporary magneto that came from the ebay engine that I have spare. All the parts that you can see had been cleaned and restored ready for refitting. Some new parts were  also ordered.


It don't take long before the magneto is all put back together again. I did not need to replace the bearings because they had only done 2,000 miles since full restoration, of course they are properly greased and checked over paying attention to ensure that the insulating gaskets are intact. It is also important to ensure that the magneto is correctly shimmed to prevent end to end float and that the armature is not binding at all. It is surprising that the magnet in this old magneto is still quite strong as there is quite a 'snatch' when revolving the armature.


The left picture shows the newly assembled magneto and the old temporary one. The crucial moment comes when I have to tighten the nut holding the clutch, fiber wheel assembly. This should ideally be tightened up with a torque wench, you might notice I make a crude jig to hole the wheel in place while I tighten up the nut, it worked quite well.

I'm not too sure if the clutch spring and washer should be greased at all. However I lightly grease the fiber wheel and re-fit the end plate. All that remains now is to fit the dynamo on top and refit the magneto to the bike. This does not take long and the timing is soon correctly set. I just need to get a better advance/retard cable as the old one is binding inside and it is also a bit short on the outer sleeve, a new one won't cost much.

I now reach the exciting part, and that is to start her up. After a few kicks and adjustments she starts. I gather it will take a little time to get used to the new settings but this is all part of the fun of owning a Classic Motorcycle. A test ride down to the petrol station and a growing nervousness as I will have to re start a hot engine. She starts will no problem at all. I had noticed that now there is a strong spark which results in the occasional vicious kick back. So probably when the carburetor has been stripped and set up properly the bike should run like a dream. Well lets hope so!

Sunday 11th March

So, How has the Magneto been behaving since it's rebuild?

Well I can say that it has been fantastic! Easy starting every time. I have really got to know the bike now. It does like to have a good carby tickle before starting however, either when its hot or cold. I have also found that she don't like the water inside her points compartment. Obviously it is an area that has to be kept dry. I complained about the bike giving a little trouble on the way to the Dragon Rally, you can read about the Dragon Rally on the Dragon Pages.

Also a similar problem to the Dragon Rally problem occurred on a trip to the BSAOC members meeting. The bike was parked outside all night during heavy rain. The next morning we set off for home only for the bike to grind to a halt after only three miles. First job after attempting to kick start the bike again, was to take out the spark plug and check for spark, Zilch! I then traced back to the damp in the points cover. I reckon that the water had traveled down the advance/retard cable. Easy job which will get done.... Eventually!



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