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Kohler on our 125 is stalling

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lrkane

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Larry Kane
Hi. Our 12 hp kohler has developed a symptom. Once in a while it would stall while mowing, as if you turned off the key. It would immediately start back up and often run for an hour or more until we finished mowing. It has now began stalling out after about 2 minutes of run time. Its not the gas cap vent, and the condenser was changed a few years ago. When it stalls the rpms go down then it dies. No chugging. I took off air cleaner to see if spraying either kept it going when it was stalling but to no avail so I think its spark related?
 

kmcconaughey

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Just because you changed the condenser a few years ago does not mean it's not failing again. Sounds like a typical failing condenser. Could also be the coil. Or a sticking exhaust valve. Or a loose head or leaking head gasket. Inspect around the head for signs of leaking gas/oil.
 

hydroharry

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David - since you voted condenser I'm going with coil. Hopefully Larry has a known good coil he could swap it with and see, this all assumes he doesn't have a leaky head gasket or loose sparkplug or loose wire.
 

mgwin

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Harry and David,
Hey, that is a company! LOL
Since you are taking the coil and condenser, I will say it is the spark plug wire heating, expanding, and losing continuity. Had that happen on my S-10 pickup.
 

dschwandt

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David Schwandt
OK, I'll cover all the bases here...
Either/or
Check for bood connections at the terminals.
I have seen wires from condensers just barely hanging on by a thread at all these locations.
Wire insulation swelling and causing separation of the wire strands within a crimp as well.
Cost me 2 mufflers on a car once. wire inside the distributor was actually severed by the crimp that went to the 2nd set of points but still making contact, that is until subject to engine heat causing the insulation to swell and pull the ends of the wire apart.
 

eweiss

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Emmett Weiss
OK, I'll cover all the bases here...
Either/or
Check for bood connections at the terminals.
I have seen wires from condensers just barely hanging on by a thread at all these locations.
Wire insulation swelling and causing separation of the wire strands within a crimp as well.
Cost me 2 mufflers on a car once. wire inside the distributor was actually severed by the crimp that went to the 2nd set of points but still making contact, that is until subject to engine heat causing the insulation to swell and pull the ends of the wire apart.
How did bad wiring cause 2 mufflers to be replaced?
 

PACub100

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How did bad wiring cause 2 mufflers to be replaced?
"Oh Oh!! Pick me, Pick me!...I know this one!"
:roflol:

Sorta like turning the ignition switch off while driving down the road in a manual transmission, counting to 3 and turning it back on....pipes filled with fumes, sudden ignition, "BOOM!!!".
Super fun when we were teens but known to test the strength of the mufflers.

🤣
 

kmcconaughey

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I blew out a snowmobile muffler back in the early 1970's, accidentally bumped the key off and quickly turned it back on- BANG! Only did that once...
 

rfunk

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[/QUOTE]
Sorta like turning the ignition switch off while driving down the road in a manual transmission, counting to 3 and turning it back on....pipes filled with fumes, sudden ignition, "BOOM!!!".
Super fun when we were teens but known to test the strength of the mufflers.

🤣
[/QUOTE]
BTDT!! Doesn't need to be a manual transmission, either. Ripped one muffler end-to-end!

However,
TEST ALL WIRES. MECHANICALLY, TOO. Sorry for the emphasis, I got suckered on that one. Got stranded, "needed" a tow home. How does a mechanical-only diesel not run?? Intermittently? Wire to fuel shut-off solenoid looked good, casual tug-test ok, BUT . . . firm tug-test felt odd. Copper core was corroded off, sometimes touched. outer part of crimp on connector was still holding on the insulation . . . "well, I know it can't run with that off, so I'll fix that before I look further . . . " Never had to look further! Could have fixed it in the cold, at night, if I'd known.
 

dschwandt

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David Schwandt
That's why I hate these original "flag" connectors on these older Cubs for the coil hook ups as they have no wrap of any kind to prevent movement,
"And", you say, "why would there be movement??"

After all, we all know these old Kohlers are whisper smooth now don't we??!!
 

eweiss

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Emmett Weiss
Yep, knew about vehicles, Just didn't figure the mixture in a small engine being able to blow a sound muffler.
 

lrkane

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Larry Kane
Ok so here’s the update. I opened up the points cover to check the gap. While turning the crank to find tdc for point gap I felt a puff of air in my face....loose head bolts. Tightened them. Started engine and watched the points spark nicely. Engine still shut down after about forty seconds of run time. Ignition wires seem sound. As stated earlier either didnt keep it going when it was trying to stall somI assumed it wasn’t a fuel problem but now not sure.I changed needle valve and seat maybe six years ago. Also changed the float. Did not change any gaskets...... ....... ........
 

mgwin

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I would definitely pull the head, clean everything, and put a new head gasket on.
If you do, make sure you run it at least five minutes to get it hot and retorque the headbolts correctly. (pattern and lbs. of torque) (y)
 

lrkane

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Larry Kane
Well it's fixed. I replaced head gasket- no change. Since the spark was strong, I replaced the carb- no appreciable improvement. The fuel line was looking a little slow even though the stock glass "filter" seemed good. SO I replaced the fuel line and filter and YES!!!!!! it runs great. So what was happening was that the fuel delivery was slower than required and once the fuel in the bowl was used up there was fuel starvation. (and now the new carb has provided a noticeable performance improvement)
 
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