On most inexpensive lawn mowers manufactured within the last 10 or 15 years,
releasing a dead-man bar on the handle both kills the engine and applies
a brake to the blade (well, actually the flywheel of the engine). In this
case, there is nothing to think about - just release the handle and it
will stop within a second or two. These are quite reliable. The usual
problem is that you forget to engage the dead-man bar and attempt to start
the mower despite the basic fact that this is quite impossible!
|NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Stopping the engine
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More expensive equipment will have a blade brake clutch meaning that while
there is still a dead-man bar but instead of killing the engine when released,
it disengages the blade (clutch) and brings it to a rapid stop (brake). This
is more convenient especially with a balky engine. There will then be a
separate engine stop switch - possibly combined with a speed/throttle control.
Equipment with an electric starter may have an ignition switch just like
an automobile and there will be three positions: STOP, RUN, START.
Some older equipment just has a stop contact that grounds the spark plug.
Pressing on a lever connects the spark plug terminal to the engine chassis
and kills the spark. While this is fairly reliable, it may be a momentary
contact meaning that the engine may be on a hair trigger and even rotating
the blade a fraction of a turn may cause the engine to take off again. Thus,
disconnecting the spark plug wire or removing the spark plug is even more
critical when working on this sort of equipment.