Old gas & how does a lawn mower generate spark & do timing?

[Nick Cine]

Took apart the pull mechanism of my single-cylinder Craftsman push lawn
mower today since it hasn't been used in a year and it wouldn't start in
one pull and the recoil spring mechanism was not recoiling after the first
pull (the cord just hung limp).

Loading Image...

When I cleaned up the recoil mechanism & put it back together, I found some
of last year's gasoline, and it worked just fine (so anyone who says you
can't use old gas is gonna have to explain why it worked just fine for me
today).

After two or three pulls with the choke locked open (otherwise it slides
shut too quickly), the motor started and after about ten seconds on choke,
I removed the clamp I put on the choke lever to keep it in place.

I cleaned out the air filter too and cleaned up old grass in the blade area
(and a bunch of rope tangled around the driveshaft - I guess slowing down
the blade is what makes the motor shut off since I defeated the shutoff
mechanism due to it being a PITA as you always have to hold it on).

Anyway, my question is I started to wonder how the spark is generated,
and I wondered how a simple (Craftsman) lawn mower advances its timing.

[Snag]

Post by Nick Cine
Took apart the pull mechanism of my single-cylinder Craftsman push lawn
mower today since it hasn't been used in a year and it wouldn't start in
one pull and the recoil spring mechanism was not recoiling after the first
pull (the cord just hung limp).
https://i.postimg.cc/xjzzBZkW/lawnmower.jpg
When I cleaned up the recoil mechanism & put it back together, I found some
of last year's gasoline, and it worked just fine (so anyone who says you
can't use old gas is gonna have to explain why it worked just fine for me
today).
After two or three pulls with the choke locked open (otherwise it slides
shut too quickly), the motor started and after about ten seconds on choke,
I removed the clamp I put on the choke lever to keep it in place.
I cleaned out the air filter too and cleaned up old grass in the blade area
(and a bunch of rope tangled around the driveshaft - I guess slowing down
the blade is what makes the motor shut off since I defeated the shutoff
mechanism due to it being a PITA as you always have to hold it on).
Anyway, my question is I started to wonder how the spark is generated,
and I wondered how a simple (Craftsman) lawn mower advances its timing.

It uses a basic magneto , a magnet on the flywheel and a coil to
generate the spark . Timing is static , there is no advance .

[AMuzi]

Post by Nick Cine
Took apart the pull mechanism of my single-cylinder
Craftsman push lawn
mower today since it hasn't been used in a year and it
wouldn't start in
one pull and the recoil spring mechanism was not recoiling
after the first
pull (the cord just hung limp).
https://i.postimg.cc/xjzzBZkW/lawnmower.jpg
When I cleaned up the recoil mechanism & put it back
together, I found some
of last year's gasoline, and it worked just fine (so
anyone who says you
can't use old gas is gonna have to explain why it worked
just fine for me
today).
After two or three pulls with the choke locked open
(otherwise it slides
shut too quickly), the motor started and after about ten
seconds on choke,
I removed the clamp I put on the choke lever to keep it in
place.
I cleaned out the air filter too and cleaned up old grass
in the blade area
(and a bunch of rope tangled around the driveshaft - I
guess slowing down
the blade is what makes the motor shut off since I
defeated the shutoff
mechanism due to it being a PITA as you always have to
hold it on).
Anyway, my question is I started to wonder how the spark
is generated,
and I wondered how a simple (Craftsman) lawn mower
advances its timing.

  It uses a basic magneto , a magnet on the flywheel and a
coil to generate the spark . Timing is static , there is no
advance  .

Difficult question about fuel. First off, there are various
'gasolines'. Large metro areas have a very different blend
(aka 'EPA gas') and summer fuel is different from winter
fuel blend. And California is different again. Generally
I've found no-ethanol fuel more stable for storage of a year
or even two. Ethanol fuel can also grow mold in fuel bowls
and lines after sitting a long while.

In short, draining the system is good practice before
storing an engine but not draining it may not be a serious
problem.