Lukas mag question

I have a 1950 fordson major with lucas magneto,my question is how to ground it to turn off tractor. I pulled front points cover,and i believe something should rotate and ground out. I also read in my manual about earthing brushes. Thank You

Theoretically, it should ground out when you retard the spark, but mine doesn't work either.
At a slow idle in high gear, I just hold the brakes and let out the clutch to kill it. Several
of my old Fordsons have had the Lucas mag replaced, so they vary. Some have external kill switches, but you have to get off the tractor to reach them. Not so good.

Hi There are a couple of lucas mags can be fitted the factory original like I have on my E27N has the advance retard linkage. (rod through the
bulkhead right hand side of steering column) If a guy isn't careful and yanks that rod round to hard it can slip the linkage on the shaft where it
enters the mag. then when you turn the lever to the stop position it doesn't ground out the mechanism to stop it. I had to adjust and re tighten the
arm to get it to work on mine as it had come loose.
If the mag was replaced with the unit they used after those original mags ran out or got expensive to buy or repair. they never had the rod and
linkage.

I have never had one of those here on a fordson. but have had similar lucas on a stationary engine and a farmall A. on those there maybe an insulated
brass screw pokes out the side, with a small spring type tab to push that grounds the mag to stop it. Or maybe you just have a screw to put a wire
on. If I remember right the A had a wire from the screw up to a switch on the steering column the wire from the mag went in one side of the switch,
the other went to ground. to stop the engine you pushed the switch and it grounded the mag internals to the frame killing the spark and stopping the
motor. maybe if you got the one that has the spring type stop on the mag you can rig the wire/ switch system off the bolt if you can find it.
Regards Robert