I'm rebuilding my '57 dominator 99, had it running early on all ok, now wiring up a new loom and find that the earth/stop connection on the magneto is already earthing to the engine body via the magneto body. This doesn't seem correct, all appears well with magneto, am I missing something here?
How are you measuring this earth? Does the engine run?
Had the engine running some months ago with no wiring connected, now fitting new loom, checked earth and cable with multimeter for continuity before connecting and found earth/stop terminal on magneto was permanently earthed. I haven't checked to see if engine still runs but I haven't fiddled with anything since it was running.
.. of kill switch do you have? Some make contact when pressed like a horn push (which you should have), others break it so are normally closed.
When you are checking, are the mag contact breakers open or closed?
Ignore the above from Colin-not relevant. Ian's comment is relevant. If you disconnect the mag kill point from the mag, and the engine runs-fine, if while reconnecting the mag kill (with engine running) the engine stops then mag kill switch/wiring does look dodgy/faulty.
My post of 27/01/2021 is still relevant.
There is no kill switch at present, white wire from loom to mag kill point, other end of wire not connected to anything, it was when I was checking continuity on this white wire that I found it was going to earth via the mag. Exhausts & tank are off at present, I'll have to reconnect to run engine to check. Thanks for your help.
Fine on latest post. I am starting to understand. You still do not say how you are testing for continuity BUT a magneto in full working order will test 'short to earth' from the kill switch point on its end cover as you are reading through the primary winding of the magneto, points open or shut. So continue to fit the loom, get lights fully working, leave mag kill wire in the 'air' if you like, engine should run, taking mag kill wire to earth kills engine. Fit mag kill switch, if it earths as expected mag will kill-engine will stop-no issue.
On talking further to Steve we have run this problem to EARTH. Measuring with a meter (or a lamp and battery) will show the resistance into a mag kill point as 'short circuit' weather the points are open or closed. So Steve had fitted the kill wire in the loom and attempted to measure the resistance. So as this cannot be measured by ordinary means we come up with some clever electronics (Advert coming up). I sell a Magneto Timing Light unit that does measure the presence of the Magneto primary winding.
... a bit of alumium kitchen foil myself - much tougher than fag paper and about .001" thick.