magneto 'kill' terminal

[Janacek]

My B31 didn't come with a mag 'kill'button, but I think it would be more convienient than using the valve lifter.
Attached a wire to the mag earth terminal and led it to earth.Tried it out earthing this wire but the engine kept chugging away.
Is the mag earth supposed to be connected somewhere else before being earthed?
There is continuity between the mag casing and earth and the earth terminal.

[idie]

If you really want a cutout on a mag dyno. You will have a mount a carbon brush on the end cap that is insulate. Then attach a wire too a button switch to earth it. I think that there was one advertised on ebay.

[Greenfield]

Magneto points cutouts are available from the Magneto Guys. Easy to fit and work a treat.

[V500]

Decomp lever is there to help kicking the engine over, not just to stop it, so unless you're going to dispense with the decomp lever (and why would you?) what's the point of fitting a mag cut-out as well?

[limeyrob]

I rode a B31 for about 10 year and it never occurred to me to try fit a mag cut out because the valve lifter does the job.  Its not easy to fit a kill wire on a mag dyno as the points run on the face cam and the centre where the brush would run moves as the points open and close.  Easy on a K2F as it has a brass bolt in the centre for the brush to run on and there's no valve lifter on the twins.

[Greenfield]

It's a bit like wet sumping. You can drain the sump before start up, or fit a tap to the oil line or fit an antiwetsumping valve.
With magneto ignition, to stop the engine you can apply the brakes and stall, or use the decompressor, or press a kill switch. You can even use a key operated kill switch for extra security. I have only fitted kill switches to MO1s and its simply a matter of swapping the points cover and deciding on a convenient place for the switch.
There isn't a right or wrong way, it's just a matter of what suits you. They all work.

[Novocastrian]

A decompression lever on a petrol engine is primarily used to ease starting, not stopping. It opens a valve that releases cylinder compression, making it easier to turn the engine over, especially with a kick starter. While some people use it to stop the engine, it's generally not the recommended method as it can put stress on the engine components

[idie]

I have been using a decompression lever for the past 60 years with no damage. How else would you stop the engine? By stalling it in gear with all the risks there is.

[Derek996]

I have been using a decompression lever for the past 60 years with no damage. How else would you stop the engine? By stalling it in gear with all the risks there is.

Agreed.

[V500]

Agreed too. Why would anyone intentionally stall it or choke it when BSA fitted a little lever for this very purpose?
There's less strain on the decomp system when holding a moving rocker up on a running engine than there is in pulling the rocker up on a stationary engine.

[limeyrob]

+1 to that.  When I used to commute to college on my B31 I came out to find it ticking over with a rather sheepish young lad next to it.  He said "I kicked it over to see how it felt, how do you stop it?"  I pulled the de-compressor.  I don't think he'd ever seen a bike with a mag and curiosity got the better of him.