[Shop-talk] It's A Simple Machine, Right?

[Jeff Scarbrough]

Update:  On Thursday, we tried a new plug - no start.  Pulled the flywheel
bolt and inspected the key - perfect alignment (did not remove the flywheel
to visually inspect the key itself).

New coil on the way - interestingly, direct from Briggs & Stratton was
cheaper than buying a B&S-labeled part from Amazon, and presumably has a
far better chance of being both the correct part and not counterfeit.


The saga continues...

On Wed, Jul 2, 2025, 14:31 Jeff Scarbrough <fishplate at gmail.com> wrote:

> I've got a puzzle...
>
>  tl;dr - should I try the plug first, skip ahead and replace the coil, or
> is there something else I should try?
>
> The patient is a Snapper rear-engine riding mower, a machine that's as
> simple as can be.  Powered by a B&S Intek 12.5 HP engine, another simple
> machine.
>
> My friend was cutting his grass and managed to get the grass chute tangled
> up in some old fencing.  He got it loose, and continued to mow.  After a
> short distance, the mower quit running and would not restart.
>
> I brought it into my shop and we started troubleshooting. I first tried
> ether - it seemed like it tried for a second, and then nothing.  Pulled the
> plug and it looked wet.  Turned the engine over with the plug connected and
> grounded, and observed a spark.  Not a magnificent spark, but a spark.
>
> Verified compression, but due to the position of the muffler, I could not
> get *any* of my compression testers to seal in the hole well.  But it
> pushed against my finger with some force.
>
> Moved to the carb.  Pulled and inspected.  Float working, jet clear.
>
> Put it all back together, and nothing.
>
> Pulled the ground wire off the magneto coil and no change.
>
> So, I'm thinking weak coil.  Not completely dead, but not working under
> cylinder pressure.  Something else I read suggested a bad plug - this one
> was installed a month ago and has been working.  Date code on the engine
> indicates it was built on April Fools Day, 2008.
>
> In the era of $15 lawn mower coils, I would throw one on with no qualms.
> But at $40 or $50, I hesitate.
>
> So,  tl;dr - should I try the plug first, skip ahead and replace the coil,
> or is there something else I should try?
>
>
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