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<p>Addendum: I'm beginning to think this might be a characteristic
of air-cooled engines (air-cooled engines have larger clearances
to begin with). I've never seen/heard a liquid-cooled engine do
exactly this but, then again, I don't recall any aircraft engines
doing it--they have dual ignition systems, maybe that makes a
difference?--and, if one did, I wouldn't fly behind it.</p>
<p>Bob<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 5/20/2019 8:54 PM, Bob Spidell via
Shop-talk wrote:<br>
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cite="mid:844aaa2e-1e86-c94c-8c9f-f8ab94c17855@comcast.net">
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<p>I had a surging problem on an ExMark--really, a tarted-up
Toro--zero-turn and they ended up replacing the engine due to
worn rings (intake manifold was getting oiled-up). Don't ask me
why, but nothing else--carburetion, spark, etc.--made sense
either. We're talking a rhythmic pulsing, and not sputtering,
right? Worn rings might make the engine's power ebb-and-flow, I
suppose.</p>
<p>Bob<br>
</p>
<div class="moz-cite-prefix">On 5/20/2019 8:48 PM, Scott Hall via
Shop-talk wrote:<br>
</div>
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cite="mid:CAK73_u5nanVpqLCZrK0UQGus2wZcyxHisYXBUvE_9_7mZcqzfg@mail.gmail.com">
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<div>This. Sounds like it's running just long enough to get a
vacuum on the fuel tank, then starving for gas. Then sitting
until the tank reaches atmospheric again. Then repeat.<br>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, May 20, 2019,
7:43 PM Pat Horne via Shop-talk <<a
href="mailto:shop-talk@autox.team.net"
moz-do-not-send="true">shop-talk@autox.team.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Try
leaving the fuel cap loose to see if that helps. <br>
<br>
Will it start up when it dies with starting fluid. <br>
<br>
Peace,<br>
Pat<br>
<br>
Pat Horne <br>
We support Habitat for Humanity<br>
<br>
<br>
On May 20, 2019, at 4:57 PM, David Hillman via Shop-talk
<<a href="mailto:shop-talk@autox.team.net"
target="_blank" rel="noreferrer"
moz-do-not-send="true">shop-talk@autox.team.net</a>>
wrote:<br>
<br>
<br>
Ok, I'm out of ideas. Requesting new ones.<br>
<br>
I have a Craftsman walk-behind mower with a 163cc
Briggs & Stratton 4-stroke engine ( engine:
104m02-0008-f1 to be precise ). It's only 3 or 4 years
old, but it will not run. And it's starting to piss me
off.<br>
<br>
It starts normally ( no manual prime or choke, so it
takes ~3 pulls but it always has ), and runs fine for
less than 5 minutes. After that, it surges rhythmically
and after a minute or so of that, dies. Following that,
it will not re-start until allowed to rest for a few
minutes.<br>
<br>
I have installed a new plug, new air filter, new
carburetor, and new ignitor. I checked and set the gap
on the plug and the ignitor to spec ( .030" and
.006-.014" respectively ). Has clean oil, and brand new
gas. Fuel screen in the tank is clean, as is the fuel
hose to the carb. Carb bowl has fuel.<br>
<br>
What else can be wrong with it? It seems to be
heat-related, but it has no cooling system.<br>
<br>
Thanks.<br>
<br>
Obligatory Shop Content: I can't work on anything
interesting until this damn mower runs.<br>
</blockquote>
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