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Have a push mower I got used. Has dead mans handle removed (kill switch was disabled). Once I replaced carb, the engine runs smooth at all throttle levels. So much so that the way the previous owner stopped the engine by dropping throttle do low does not work. It just idles slow.

I am handy enough to do basic work on small engines, but novice to some things. This being one of them as I have never had to deal with it.

So after pulling the top I found the following....


Looking at the kill switch set up. Pic 1 is loose wire running from box linked to spark plug. Pic 2 and 3 is how they had tied the handle lever in run position. Finally pic 4 is the switch itself that loops back to a cut end. I assume the original loose wire in pic 1 was connected to the cut end of the wire leaving kill switch.

My question...
If I assume right do I just put a new switch between/connecting the loose wire in pic 1 to the cut end of the wire in pic 4 and leave the lever tied together as in pic 2/3 and use the new switch to complete or break connection thus stopping engine.

Never added a kill switch. Any advice or diagram would be great.

There are two key parts to safely stopping a typical mower engine:

1. Killing the spark.
2. Applying a brake the the flywheel. (this ensures the blades stop spinning < 2 seconds after you let go of the blade control lever)

When you hold down the blade control lever on the handlebar, it pulls a cable, which pulls the brake pad/arm away from the flywheel and also presses the plunger on a small switch. When you release the lever, the spring snaps the brake pad against the flywheel, and the plunger on the switch is released. The switch is normally CLOSED, which means when the plunger is OUT, the terminals ARE connected, and this makes a connection between the ignition coil and ground, killing the spark. When the plunger is pressed IN, the switch is OPEN and the ignition coil is NOT grounded and can fire the spark plug.

The wire (pink highlights) runs from the ignition coil to the backside of the engine stop switch. Confirm the plunger is press down fully when the blade lever is held down, and the plunger is released fully when the blade lever is released. The cable attaches at the purple highlight:

Thanks for the diagram. It seems I am looking at all the parts correct.

Since the blade control lever was removed before I got it, would an external switch placed between the front terminal wire and back switch wire work if I leave the break wired open from fly wheel AND the plunger on the switch all the way in to engage the blades? Would this work or am I not thinking about something that would cause that not to work?

If not, other than trying to et my hands on a blade control lever and cable system, is there a way to just add a switch to kill ground the engine?

Vanousb said:

Thanks for the diagram. It seems I am looking at all the parts correct.

Since the blade control lever was removed before I got it, would an external switch placed between the front terminal wire and back switch wire work if I leave the break wired open from fly wheel AND the plunger on the switch all the way in to engage the blades? Would this work or am I not thinking about something that would cause that not to work?

If not, other than trying to et my hands on a blade control lever and cable system, is there a way to just add a switch to kill ground the engine?

Click to expand...

Technically, any method of grounding the ignition will stop the engine. But, that's still not a safe mower. The blades will keep spinning unless a brake is used to stop them quickly. I'd strongly recommend you contact a Yard-Man dealer and get the correct blade control lever parts/cable and get the blade brake working properly.

On mowers that fully stop the engine, the grounding switch is normally CLOSED (contacts closed when plunger extended). This is so a human must physically pull back on a control lever, causing the switch plunger to be pushed down, forcing the contacts OPEN, and break the ground, so the engine can be started. If any part of that fails, the contacts will close and the ignition will be grounded an "no start."

Robert, I appreciate the info. Have ebayed at low cost a handle lever original part and brake control cable. Looking for a throttle control box. Agreed with you and decided not to short cut. Like to get it close to original as much as possible.

Here's a failure that goes in reverse. Release the "dead man" bale and the engine KEEPS RUNNING. Is it possible to jam the switch OPEN? I have to cut off the fuel with a valve I put in before this started happening. I can cut about 200 linear feet before the engine quits. The flywheel brake seems to work right...full stop in 1 to 1.5 seconds. De-compressive start also seems to be fine. Mower about 8 to 10 years old, stored in air conditioned garage.

Brian D

Mobile

bd64kcmo said:

Here's a failure that goes in reverse. Release the "dead man" bale and the engine KEEPS RUNNING. Is it possible to jam the switch OPEN? I have to cut off the fuel with a valve I put in before this started happening. I can cut about 200 linear feet before the engine quits. The flywheel brake seems to work right...full stop in 1 to 1.5 seconds. De-compressive start also seems to be fine. Mower about 8 to 10 years old, stored in air conditioned garage.

Brian D

Mobile

Click to expand...

The kill mechanism is not moving with the bail cable.

Check for freedom of movement when the bail cable is pulled and released.

It goes 200 feet because it takes that long to vibrate and move to the kill position.