Mower dies after running for 20-30 minutes

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My Zero turn was doing the same thing. Mine has vent line going to a canister under the seat. The vent line was made out of some cheap plastic and would pinch itself shut. I replaced it with some rubber fuel line and not had an issue since.
 
Had a similar issue the other week. Was going across the yard about 20 minutes in and wondering why the last few passes had a shiny stripe in the grass. Then immediately felt the engine start bogging like things are about to stop spinning inside. Apparently a 27HP Kohler has a second oil drain plug I've never seen and it is now somewhere in my yard. 3/8 pipe plug, Loctite and some Lucas fixed her right up.

Yours sounds like a fuel pressure/delivery or vapor lock issue.
 
braxton357 said:
I'm not reading that long ass post, but I bet the valves need adjusted or you have a sticking valve or bent push rod. Also I have some of those gaskets for that fuel gauge, I have to replace them every couple years
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Hahaha, you suck. :flipoff2:

The gaskets aren't leaking, the weephole is:
I'll probably just put a dab of JB weld on it. Then I can see that the gaskets are also leaking ;)

I definitely should check the valve clearance. Haven't done that in 4-5 years of ownership.
 
braxton357 said:
I'm not reading that long ass post, but I bet the valves need adjusted or you have a sticking valve or bent push rod. Also I have some of those gaskets for that fuel gauge, I have to replace them every couple years
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My briggs bent 3 pushrods before I realized the valve guide had slid out of the head slightly causing problems. I taaaaaaped it back in, staked it and hoped for the best.
 
My mom's mower did kinda the same thing but probably not what you're experiencing, still worth a mention. A wasp corpse was floating around the bottom of the tank and would occasionally make its way to the hole in the tank nipple, occlusion it under suction from the pump. Engine would die, suction would stop and the dead body would be released from the hole. Crank it back up and it would be good until it made its way back to the hole. Sometimes immediately, sometimes the next mow.

TLDR: Feed the pump from a known clean can to eliminate a tank issue.
 
Ok, so some more diagnosis after it doing the same thing again last weekend.

Takes starting fluid to get it running, once running it runs fine for about 15-20 minutes, then starts to die, if I quickly go full choke it runs another 30 seconds or so, then dies and won't start back up. Immediately when it died this time a pulled the fuel supply line to the carb and confirmed it is pumping fuel. Then checked spark and there is good spark on both plugs (I had a theory in the back of my mind that voltage was getting low and the spark was weak or non-existent). Opened the carb float bowl drain screw and good clean fuel ran freely out. Air filter is reasonably clean. Pulled the carb and it's clean as a whistle, jets are clear, no residue, float moves freely. Verified function of the fuel shutoff solenoid and it works great, both on a 12v supply, and when plugged in to the mower harness. Once it cooled down, I checked compression and valve clearance:
Left side
85psi
Intake 0.025"
Exhaust 0.000"

Right side
120psi
Intake 0.000-0.001"
Exhaust 0.020"

Spec is 0.004-0.006" for both, so I set them all to 0.005" at TDC, and compression changed to right at 90psi on the left and 95psi on the right cylinder.

Machine has a little over 2000hrs on it, so I'm wondering if its just wore out. Also, Kawasaki has a TSB on the heads and cam for this motor, so maybe that has something to do with it, but at 2k hrs, I don't even know if it matters...
 
is the float filling up with fuel?
 
This is a long shot, but check the magnet on the flywheel to see if it's still good (should attract a slotted screwdriver from 1/4" away easily), then insure that you have .010" clearance between the coils and magnet (a business card works well). Lastly, and this one requires some ingenuity or the correct tool, but make sure the coils with spark across at least a 1/4" gap.
 
maulcruiser said:
This is a long shot, but check the magnet on the flywheel to see if it's still good (should attract a slotted screwdriver from 1/4" away easily), then insure that you have .010" clearance between the coils and magnet (a business card works well). Lastly, and this one requires some ingenuity or the correct tool, but make sure the coils with spark across at least a 1/4" gap.
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Yes, a couple weeks ago I regapped the coils because I was initially suspicious that it was an electrical issue. Also cleaned all the surface rust off. Magnets were good and strong, gapped with a business card, haha.

When it died this weekend, I checked the plugs with a test plug that has a ~3/16-1/4" gap like this:
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The only other thing I can suggest from my seat here at the computer is to disconnect the kill wires from the coils themselves. With that said, I cannot stress enough how "unsafe" this is because all of the machine safeties will be disabled, and the ignition switch will not even stop the engine until they're reconnected or it runs out of fuel. If it continues to run with those disconnected, we can go back to the mower being the problem, and not the engine. There may be a module or safety that is failing, or simply an ignition switch that is finding a circuit to ground.
 
grapehead said:
vac leak that appears when warm?
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Maybe, but I'm not sure where to look since I've already replaced all the lines. Will definitely replace the fuel pump, even though I'm 95% sure that's not the problem. And it pumps fuel right after the mower dies when it won't start back up. And there is fuel in the float bowl.
 
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