The recent thread about fitting a cut out to a magdynamo mag immediately sprang to mind when I spotted this on e bay....

First thoughts....Clearance between the mag and the back of the chain case may be an issue on some bikes....

... 281804956711 ....Ian

email (option): ian@wright52.plus.com

yeah it looks nice...............

i never investigate a cut out,but in my thought,there is a ground brush fitted in the magneto,when you remove this one,will the spark than be gone???
in that case you can make an insulated nut with a wire fitted to the brush.
make a normaly closed switch on your handlebar,push the button and the spark will be gone.
am i right about this???

email (option): roy206@hotmail.com

It certainly won't fit on a 16H...The points have to be in just the right position to get the standard cover on as it is.

Sounds brilliant. Does anyone have any past experience, good or bad, with "The Magneto Guys" or know who they are?

email (option): jonny.rudge@verizon.net

WHY...I never had a problem stopping mine, starting yes...If you want a way to stop the engine just bolt a piece of metal about an inch wide with a hole one end to put the head bolt through the other end bend over so its just above the spark plug top then put a bit of rubber on the end to stop your eyes lighting up when you push it down on the plug top, worked great on my old lawnmower.
will not work if you have put a Bakelite top on.....If you try to fit a cut-out via the mag you must remember it must have a good ground while running...sounds like a breakdown waiting to happen not to mention mag damage....What's next lights, so you can see where your going !!!!

email (option): richard.a.yard@btinternet.com

Well, my Triumph TRW has one fitted as standard (so do a number of other twins and singles) and I'm not aware of it leading to premature mag failure....

As it's hard to get to the carb (impossible with the air filter connected)and the bike is set up to tick over, the little press button on the nacelle comes in pretty handy..Ian

email (option): ian@wright52.plus.com

As does all Speedway and Iceracing Jawas that has magneto ignition. Never heard of them malfunctioning either

Interesting thing Ian!

Sorry Lads silly me I thought the thread was about Retro-Fit cut-outs for road bikes not factory fitted cut-outs, if we are talking factory fits most motor cycles and scooters had mag ign up to and after 1980s with cut-outs of course they did not fail very often
Silly me...

email (option): richard.a.yard@btinternet.com

I was referring to what you wrote about a cut-out switch as a possible cause for magneto damage/failure. I perceived this as though you meant that this would somehow be happening, which I did not quite understand. Therefore I mentioned some bikes that has this feature without magneto failure.
I fully agree with you that such a switch comes with an increased risk of problems due to short circuit and other electrical issues. Some might think the pros outweigh the cons, some not. To each his own.

A 'factory fit' mag cut out is basically the same as a 'retro fit' cut out...

Operating in the same place, doing the same thing the same way....With the same potential for faults, or not...

The factory fitted examples are as simple as it gets and not difficult to replicate....Ian

email (option): ian@wright52.plus.com

The biggest probelm area is the switch that puts the low-tension to earth.

We discovered that often they failed - on at certain rpm.
Intially on a manx, then we had same problem on the Yam's, both only spotted while running on a dyno - we came to the conclusion that the contact (usually a stip of metal) was resonating at certain rpm.

So we used speed-way ones which are basically a lanyard attached to an insulating clip - positively holding the switch open - until the clip was removed.
Worked well, but the lanyard was a hassle.

Eventually we started using jet-ski switches - we also filled them with silicon grease (seemed to damp the resonance) - which is what we still use.

A major problem is the dire quality of the after-market ignition cut-out switches, compared with OEM switches - they are usually just a horn switch. Though even these can be improved by filling with silicon grease.

And yes they are damn handy - also a neccesaty if you want to do a proper 'plug chop'.

Good Day All,

Back to Ian Wright posting on Magdyno Cut Out Switch dated Oct 2, 2015, this is my version that currently attached to my machine, BSA M21 1958. The fabrication is by D.I.Y ( do it your self ) and the cost impact is less then 5 quid.It's just enough clearance here between the mag and the chain case.



The principle of it :
To cut out the LT (Low Tension) current by ground it to the body via carbon brush that touch the contact point breaker arm fitted to the contact point cover using nylon nut, nylon bolt and sleeves as the diameter of the carbon brush.

The carbon brush was machined from normal carbon brush used for electric power tools by turning it using hand drill and small file to form it from square to round and to the size required.Mine is 5mm in diameter.




From the carbon brush with spring loaded, it will connect to a wire and grounded to a normally closed for a key switch and normally open for push button kill switch.

email (option): roslansubri@gmail.com

Nicely done!

email (option): teladelujo@msn.com