Magneto earth terminal

[les.brooks]

Just assembled my VB basket case, mag has been rebuilt and I have had the engine running, the dynamo is in place but none of the electrics are in place. I have no experience of mag dyno set ups so my question to those that have may seem too obvious, how does the mag earth terminal need to be connected?

[simon.holyfield]

You mean the one on the end of the points cover? You can leave it disconnected, and stop the engine with the decompressor, or you can wire it to a cut out button on the handlebars.

Earth it and the engine will stop.

[les.brooks]

Thanks Simon

[keith.mettam]

Les I believe the earth terminal you are referring to is the one on the points housing body which helps fix the points housing to the magneto body. The singles don't have an engine cut-out terminal on the points cover, normally relying on the handlebar exhaust valve lift lever to stop the engine. However, the terminal on the points housing body is generally used for testing purposes, I think, but there is no harm in permanently connecting an earth wire to it which will help ensure good earthing of the assembly although this is not usually necessary or normally done.
Regards,
Keith.

[paul.jameson]

The main use of the earth terminal on the points plate (not the end cap) is to earth the magneto and dynamo to the frame. If you have repainted your magneto platform you have a good chance of an intermittent earth connection between the magneto body and the magneto platform engine plate. Many an Ariel owner has been somewhat stumped when his bike has suddenly lost sparks a little while after the rebuild, despite having run satisfactorily for a while.

If you have had the magneto platform powder coated I would run an earth from the earth terminal to the frame earth and another from the earth terminal to a cylinder base stud. You will also need to tighten the magneto bolts several times as they bed in. When the magneto platform is painted, the paint (or powder coating) compresses with use, the bolts come slack and fall out and then the magneto chain jams causing all kinds of problems.

Personally, I never paint or powder coat the magneto platform but I have still had earth problems on a newly rebuilt bike.

[les.brooks]

Thanks for all these replies, I've checked the earth and yes it's on the mag body so an additional earth point. I would have liked to have connected up an ignition switch to kill the engine does anyone have any suggestion how this could be done?

[pete.collings]

See Ebay item 282010852530

[les.brooks]

Thanks Pete

[les.brooks]

Made one up myself, works well.