On Apr 13, 8:15*am, "Stormin Mormon"
wrote:
Usually, the Tecumseh allignment key is soft metal, and is
sacrificial. You hit a rock, the flywheel is now out of time
with the cylinder stroke. On the points ignitions, you lose
spark. On the electronics, you still have *spark, but it's
way out of time.

Maybe you need a softer flywheel key?

--

I agree, I an thinking about making my own from aluminum. I have no
idea why this model uses the steel key, but I think it is a poor
design. If the flywheel has to be aluminum for the OSHA nazis, then
at least press the thing on to a steel hub so the key will shear
rather than eating the flywheel. The more common flywheel has a wider
slot and the key is some sort of die cast material. I went and tried
one of these and my mower wouldn't start. I was unaware that mowers
with light flywheels rely on the blade being attached, so when I tried
my parts swap, I was without blade so I assumed that the timing was
set different on the two models of flywheel. Now I am not so sure,
but I think I am going to test it when I have both sitting in the
driveway.

I am also informed (but I am not sure of the reliability of the
informant.) that mowers were detuned to meet emission requirements by
retarding the spark. If I have the ambition I might play a bit with
the timing to see if I can improve the situation. This of course is
going to mean making my own timing marks and some how making an
adjustable timing set up. Perhaps I could cut down the two bosses
that the ignition module sits on and make a little plate so that the
module could be adjusted like a distributor on a car. It might be
that I will end up with a set up like the Model T where you pulled the
spark lever back to start the engine, and then advanced it to run.

Another way would be to do it like they do now on the newer cars, a
halls effect sensor could pick up the crank position, calculate the
rpm and the optimal time to fire the plug. (I probably sound like a
guy with too much time on his hands. Mia culpa!)

Yet another way would be to mount the flywheel without the key,
relying only on the taper to keep it in position.

Of all these schemes, I think the first may be the best even if the
run timing is not changed if you spring loaded the plate a cable could
then be run to the handle to retard the spark even further to make
starting that much easier.

Roger Shoaf