Lawnmower gets hot and quits

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My 4 year old lawnmower gets hot and dies. I can mow for 15 minutes and it coughs and sputters and then shuts down completely and will not restart - for 15 minutes. Then it will start and runs another 10 minutes.
Seems to be a heat related issue. I cleaned out the debris and replaced the spark plug. No change.
What could be wrong and how do I determine it?
Sherman
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Right after it sputters and dies, will it start again??
If not a shot of either, if it turns over and runs for a moment then its not the spark.
What you have sound a lot like its starving for fuel.
Before ripping apart the motor (like other suggested) I'd recommend just cleaning out the gas tank (there should be a strainer filter in there) check and possibly replace the fuel line (you can get more fuel line at your local auto store) Some carbs have a bowl on the bottom of them, you can take that off and clean it out.
Take a look at your air filter, make sure its happy too!
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Diving down from center field...
Does the engine have an oil sensor? What is the oil level and when was it changed last?
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you didnt say if it is push or rider and engine you have,that would narrow things down
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add more coolant to the radiator.
wrote:

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I like Rick's gas cap vent possibility. Maybe it's not getting too hot, but building up a vacuum in the gas tank. It shuts down and then takes a few minutes to slowly equalize the pressure before it'll start again. What the hell, take the gas cap off and see what happens.
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replying to JWitherspoon, Marc Belanger wrote: he said it will only run again when cold. Mine is doing the same thing as his, it is the coil. when it gets warm, the coil opens and doesn't give spark. When it cools back down, the coil fires the spark plug. it won't even sputter when it gets warm, when cold, starts right up everytime
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On Fri, 24 Jun 2016 20:44:02 +0000, Marc Belanger

hot fouling plug, hot-failing plug wire, and heat sensitive loose coil mounting???? On electronic ignition mower engines it is almost always the coil - except on those rare engines with a separate ignitor - where the ignitor itself may be bad and the coil still good (although USUALLY it is a bad coil that kills the ignitor module). On older point ignition engines it CAN be a bad capacitor (condensor) or a bad coil.
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replying to JWitherspoon, Bob wrote: Ancient thread, I know. But thank you, thank you, thank you for the gas cap vent idea. Cured my problem immediately.
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Lots of things...
But check for spark next time it happens-if not, you need a new magneto coil. That's about $40
If it has a primer bulb, see if it's collapsed-could have a plugged pickup tube screen in the gas tank. You drop the tank to clean that
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Oh yeah-check the vent on the gas cap, too. Do the simple things first...

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Rick says "Check the vent on the gas cap, too".
Well, Bingo! Rick wins.
After checking for spark after it died, and getting a positive response from my wife on spark, I replaced the spark plug cap and reached up untwisted the gas cap off a 1/4 turn and it started on the first pull.
Now, I looked and I don't see any hole in the gas cap for it to vent. I hate that she has to mow with the gas cap not tight. She might catch the mower on fire. I'd hate to lose that old mower.
Do I just drill a small hole in the cap?
Sherman.
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Sherman wrote:

It's a four-year old mower and <now> a non-vented gas tank is the problem? Don't think so... :)
Mayhaps the vent is plugged, but I'm still not convinced...there's got to be an existing vent if that is the problem or it wouldn't ever have run reliably...
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On Wed, 20 Jul 2005 14:36:14 -0500, Duane Bozarth

The cap is hard rubber with a rubber washer that has 2 small holes in it. Behind the 2 holes is another flat thin rubber washer that has deterioated and the deteriorated rubber is actually protruding partially thru the tiny holes. I suspect it completely stopped up the vent holes.
I tried removing the deteriorated rubber, but can't really get to it. If she comes in bitching about the mower dying again, I'll add a new vent hole thru the cap.
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Seems like a lot of work for one guy. She's cutting the grass so it is her responsibility to take care of the dammed thing. Tell her to drill the hole.
Be sure to report back with the results when you do!
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Ed, he won't be able to sit down to type with that drill up there...
--
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On Wed, 20 Jul 2005 14:36:14 -0500, Duane Bozarth

You are right. The vent is plugged.
The cap is hard rubber with a rubber washer that has 2 small holes in it. Behind the 2 holes is another flat thin rubber washer that has deterioated and the deteriorated rubber is actually protruding partially thru the tiny holes. I suspect it completely stopped up the vent holes.
I tried removing the deteriorated rubber, but can't really get to it. If she comes in bitching about the mower dying again, I'll add a new vent hole thru the cap.
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Sounds like a valve clearance problem to me. Either that, or the fuel line is too close to the engine. But more likely valve clearance.
I took a small engine repair course years ago. To fix this, you have to take off the motor cover, the cylinder head, and then remove both valves. Grind a little off the bottom, ch eck the clearance, and put it back together. Requires some specialized tools, and some replacment gaskets.
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Stormin Mormon wrote:

That sure wouldn't be the first place I'd look....more likely electrical as someone else noted w/ thermal expansion...besides the magneto, it could also be the plug ceramic...(look, look)...oh, I see he did change the plug so it's upstream of there...
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I may well be misaken. But I've seen valve clearance problems several times before. Though, coil problem is a bit easier to fix. How about find another coil to try for awhile?
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Christopher A. Young
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