On Sat, 27 Apr 2024 17:23:25 -0600, Nick Cine <nickcine@is.invalid>
wrote:

>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.
Spark is produced by a flywheel magneto - later ones have electronic
trigger built into the coil - old ones had points and condenser.
Timing is fixed on MOST smalkl engines. The odd one MAY have
elecctronic spark retard designed into the coil trigger circuit