How to make a kill switch?

2door said:

But it would still work today. That's the beauty of 'old things'. They work.

And, we don't know the vintage of the OP's engine. A Briggs flathead could be older than me, and that's old.

Tom

Click to expand...

And I've done it that way a couple times on older engines, WTF, IT WORKS!!!
fatdaddy.

After looking at Jazz's build pics, it looks like he has a pre-1986 briggs with points & condensor ignition.

The first step should be conversion to solid state ignition. There are 3 ways to do that.

1) Replace the old coil with a new Magnetron coil which is self contained.

2) Use the B&S upgrade kit with the small module that snaps on the original coil.

3) Use an aftermarket module like the Nova II.

Obviously the new coil gives you a complete new ignition system. Import replacements are around 25 bucks. OEM stuff about 45 bucks.

The Nova II would be my second choice if the coil is in good shape, and the high voltage cable is not cracked. Easy to install, and very reliable triggers.

One other thing to address on the old recoil Briggs like that is the start clutch. The balls need to roll freely - clean with no grease or oil.

The long shaft under the square section does need lubrication. There should be a felt plug in the end of the recoil square section to hold oil. many have a pinhole in the end of the square section to add oil occasionally. A drop or two of engine oil is usually enough.

If the recoil clutch seizes on the crankshaft it gets ugly quick. The recoil turns the wrong way, breaks the pull rope and sometimes other things attached to it as well...

.

If you cant find any wires, solder a wire at the top of the spark plug wire (Where it goes on the plug, run that wire to a toggle switch and run the other end to a head bolt or something.

TakeiT said:

If you cant find any wires, solder a wire at the top of the spark plug wire (Where it goes on the plug, run that wire to a toggle switch and run the other end to a head bolt or something.

Click to expand...

Not a good idea, that is spark plug voltage!

What you want to do is simply ground the magento output BEFORE it even gets to the CDI that boosts the voltage up to spark plug voltage.

What is ground?
Your engine case.

The magneto has 2 wires and every circuit needs a + and - , one side of the magneto output just connects directly to the engine case.
That is ground and how your spark plug can fire with just one wire, the other wire (usually blue) is the magneto output to the CDI input.

Short out the magneto output and it won't run.

I feel a momentary kill button is crucial right there on the throttle for emergency engine kills, but you can also put switches anywhere else between the magneto output and CDI input to kill the engine and prevent it from even starting.

I have done this a lot on 2-stroke builds by putting a KeyLock switch right on the CDI itself to short the magento output out before it can enter the CDI.



That is key operated electrical switch, but just a 2 pole switch none the less.
It's open or closed.
Closed grounds the input wires and the engine won't start, open the switch and it does, it just takes a key to 'flip' this switch is all ;-}

Heck, you can just use as many toggle switches anywhere between the magneto and CDI you want, it only takes one to keep your engine from starting and that sure makes it harder to steal.

Sure someone can steel it by pedaling away, they just won't be able to start the engine to hep with the get away.
Also handy if you don't want a family member to take it for a ride.

Anyway there are lots of ways to kill a running engine and prevent it from starting, ground out the magnetos output before it gets to the CDI.