[Shop-talk] B&S mower engine, surging and dying. Ideas?

[Battmain battmain]

If there is a fuel shutoff valve, bypass it and see what happens. The plastic valve I removed from a similar engine has not yet been re-installed. The engine starts on the third pull everytime and doesn't shutdown until it is out of fuel or I switch it off. I do have to empty any left over fuel if I screw up and put too much in the tank.

Brian


On May 21, 2019 00:25, Bob Spidell via Shop-talk <shop-talk at autox.team.net> wrote:
>
> 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.
>
> Bob
>
>
> On 5/20/2019 8:54 PM, Bob Spidell via Shop-talk wrote:
>
> 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.
>
> Bob
>
> On 5/20/2019 8:48 PM, Scott Hall via Shop-talk wrote:
>
> 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.
>
> On Mon, May 20, 2019, 7:43 PM Pat Horne via Shop-talk <shop-talk at autox.team.net> wrote:
>>
>> Try leaving the fuel cap loose to see if that helps. 
>>
>> Will it start up when it dies with starting fluid. 
>>
>> Peace,
>> Pat
>>
>> Pat Horne 
>> We support Habitat for Humanity
>>
>>
>> On May 20, 2019, at 4:57 PM, David Hillman via Shop-talk <shop-talk at autox.team.net> wrote:
>>
>>
>>   Ok, I'm out of ideas.  Requesting new ones.
>>
>>   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.
>>
>>   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.
>>
>>   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.
>>
>>   What else can be wrong with it?  It seems to be heat-related, but it has no cooling system.
>>
>>   Thanks.
>>
>> Obligatory Shop Content: I can't work on anything interesting until this damn mower runs.
>
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