My 129 powered down suddenly while mowing and can't get it restarted
 

It was going along great. Hasn't run since last fall, but started right up. I wondered about possibly overheating (are those old ones thermally regulated somehow?) but after letting it sit for about 20 minutes, it cranks fine but won't start. It almost seems like it wants to start right before I turn the key back off, but then won't. Have to wonder if it's a sudden fuel delivery issue. Started raining awhile ago so I won't get to do anything with it till I get the local farmer to help pull it out of the woods with one of his 4-wheelers. Thanks for any suggestions on what might have happened with it.

Quick update: Went back down in the woods and got it started. It's running very rough though but I'd say the engine sounds fine otherwise. Possibly a coil or other electrical issue? Now that I have it back in the garage I can start checking a few things. I'd not feel safe taking it farther away from my property the way it's running now. Once I got it back in the garage, it didn't want to start again.

don't tow it fast and release the hydro relief valves if they are not automatics, tow it too fast or far you risk ruining the hydro, do you have fuel at the carb and spark ? 3 things needed to run,air (compression ) fuel and spark ..:beerchug:

Luckily didn't need to tow it, but haven't done anything since other than start it up the next day - seemed to run fine with just an occasional dip in the rpm. Governor seemed to be operating fine. Most interesting, though, is that in going back through my older posts I saw that I started a thread describing this exact same issue two years ago: https://www.onlycubcadets.net/forum/...ad.php?t=62474 Once everything seemed fine, there was no need to follow up in the thread, and yet now here I am again reporting the same problem. The previous time, though, it started up after only 5 minutes or so. This time it took closer to a half-hour. I'm a bit hesitant to use it back down in the woods again for fear of getting stranded. As you point out, have to be careful how it'd be towed.

My opinions (fwiw):

Theory #1
You have a gas shutoff (#6) that threads into the fuel tank.
The yellow highlighted part of the valve is a very fine screen filter.
There is crap in the tank and because you are running and draining fuel,
the crap collects on the screen and chokes off gas flow, engine dies.
After a rest period, the crap floats away from the screen, fuel flow resumes, engine starts.

Remedy - remove tank, remove valve from tank, clean valve screen, flush out tank.

Theory #2
You have a fuel cap on the tank (#4 in blue). The cap has a vent hole on top and a baffle underneath on the inside.
The vent allows equal air pressure inside and outside the tank.
Dust and dirt has built up in the vent hole or baffle preventing equalization.
As the engine runs, gas is being sucked out of the tank and no air is getting in through the vent.
A vacuum is created in the tank and fuel flow stops, engine dies.
After a rest period, the vacuum depletes, fuel flow resumes, engine starts.

Remedy - Remove baffle from cap, clean baffle and cap vent hole.

Ironman...thanks. Both great suggestions. Haven't had the tank off and cleaned out for quite some time. Petcock was replaced a few years ago. I had the gas tank cap off and made sure the vent hole is open but didn't do much else with it. Right now I'm involved with the pulley hub set screw issue that I just posted about. I knew something didn't sound right at the front of the engine when it tried to start lately. Looking back in my repair notes I see that in '87 I ran into an issue where BOTH drive hub pulley set screws were gone. I'm betting your theory #1 could well be the problem. I replaced the fuel filter today as part of my annual maintenance, along with the plug and air filter. Still have to change the oil and trans filter, take off and clean the deck, take off the blades and sharpen, etc. Gettin' too old for some of this stuff. That deck gets heavier to move around every year.

What surprised me today, though, is that I couldn't get it started at all. Didn't expect that. Seems like it wants to start right at the end each time but then sputters out. Something's just way off it seems. Hasn't been this balky since I replaced the engine several years ago.

In looking back at my earlier thread dealing with this same issue, I'm curious about the one reply: "In my limited experience, fuel delivery problems are usually not a instant dead stop problem but one where the engine starts to starve,then changes pitch, runs hot, sputters, then dies". This makes me wonder about whether it is a fuel issue or something else that would have caused it to shut off immediately with no indication of starting to gradually have difficulty. Running completely normally the one minute, and then suddenly shut off.

bad wire /broken wire between coil and points ? possible coil issue ? sounds electrical if it just shuts down ?

My vote is for the coil.
Had the same thing happen to me while mowing cemetery with a Q/L several years ago.
Wound up being the coil.
Gets hot then shuts down.

I've never done any work with these other than replacing them. Easy way to test with multi-meter? The coil is roughly 10 years old based on my notes of when various electrical components were replaced. Came across this by googling. Most videos don't show testing the older style canister coil but rather a more square unit. I suppose the procedure is the same.

1. Check for Spark
Before testing the coil with a meter, verify if it is producing a spark at all:
1. Disconnect the spark plug wire and remove the spark plug.
2. Reconnect the plug to the wire and lay the threaded metal part of the plug against the bare metal of the engine block.
3. Crank the engine over and look for a bright, snapping blue spark. If there is no spark, proceed to the resistance tests.

2. Test Primary Resistance
This measures the resistance in the smaller, initial winding of the Coil:
1. Disconnect the positive and negative wires from the coil.
2. Set your multimeter to the lowest Ohms (resistance) setting (e.g., 200 S2).
3. Touch the red probe to the positive (+) terminal and the black probe to the negative (-) terminal.
4. A healthy Kohler ignition coil usually reads between 3.2 S2 to 4.7 9

3. Test Secondary Resistance
This measures the high-voltage winding that travels to the spark plug:
1. Set your multimeter to a higher Ohms setting (e.g., 20, 000 S or 20k S2).
2. Touch the positive probe to the positive (+) terminal and the negative probe inside the spark plug wire terminal (or touch the metal tip of the spark plug wire).

here is info from our tech section on testing the Kohler coil :

https://www.onlycubcadets.net/forum/showthread.php?t=11

If you buy a coil ,make sure you get one that has the internal resistor .