Lawnmower gets hot and quits

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Stormin Mormon wrote:

How about checking for spark when hot first, as has already been suggested (several times)????
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What makes for less clearance after 4 years of running? I'd have thought the opposite would happen. Or is it worn on the stem and not contacting properly so relieving the valve seat brings it back?
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wrote in message

have to

valves. Grind

together.
thought
contacting
No, the valve seat sinks into the block. There's supposed to be a little clearance between the lifter and the tip of the stem, so you grind the end off. That's for the more common valves in block type., not on an OHV..
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wrote in

Or the seat and the valve face wear. In that case, seat and valve regrind or replacement....
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Have you tried cleaning or replacing the air filter?
--

Larry Wasserman Baltimore, Maryland
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wrote:

This is a push mower Craftsman about a 4 hp.
I removed the gas filter bowl and it was clean. No change after cleaning and reinstalling. Started right up and ran for 10 minutes..
After it dies hot, it will not start or even try to start. The pull compression feels about the same hot or cold. But I can't measure the vacuum (or can I?)
Has to cool down and at some point it cools enough to start on first pull and runs good for 10 minutes.
I will check for spark next time it is dead.
Sherman
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I fail to see the problem. With a strategically placed cooler of beer, you are being forced by nature to take appropriate breaks. This is for yourgood health.
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wrote:

Actually, I lied. My spouse does the mowing and she is getting angry at me because the mower is dying. Don't get me wrong, I will mow when it needs it, but in 30 years, she has never let it get long enough to need it.
I need to get this thing diagnosed and fixed pronto.
I'm thinking I could use one of those piercing shroeder valves on the intake manifold to measure for vacuum while I yank the rope. Wonder if it would work. Or I could test compression thinking maybe the compression would be different if the suction was off due to valve not seating..
Sherman
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Sherman wrote:

Your wife mows? Get her this: http://www.cleanairgardening.com/brillux38ree.html
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wrote:

Ok, I'm also thinking I could pull the valve cover and observe the valves when hot or cold. What am I looking for? As the crank lets the valve close, it should become loose and I should be able to grab the stem and lift and let go and hear the valve seating - right? It would probably be a different sound if it was not seating.....
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Sherman wrote:

If they're not seating, you won't have compression when you crank...
Did you find out if you have spark when it's hot or not yet? I'm still thinking electrical is more likely the culprit...
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Forget the damn valves, that's not the problem. You've been given sound advice by several people: check to see if you have spark when it's hot and not working. I'm betting you don't, because the magneto has failed.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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replying to Sherman, D Mecate wrote:

Until the electrical issue is addressed, you're simply fiddling with parts that are more than likely functional; change out that ignition coil.
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wrote:

This is an outside possibility, but I had a lawnmower with a leaking head gasket. Problem was it would leak only when the engine was hot. The problem was getting worse and worse and I could not figure out what was wrong. The gasket finall degraded to the point that that when I happened to brush my hand ove the head, I could feel the hot gases leaking from the head gasket. Gary Dyrkacz snipped-for-privacy@comcast.net Radio Control Aircraft/Paintball Physics/Paintball for 40+ http://home.comcast.net/~dyrgcmn /
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Sherman wrote:

Many, many air-cooled engines develop this problem. The odds are overwhelming it's your ignition module, and they're a bastard to troubleshoot [except, of course, by replacing the module].
As soon as the engine starts to cool -- long enough to check for spark -- the module cools down enough to check as OK. It's very possible you'll check the spark and it'll be OK.
They're easy to change, but shop carefully. The price for replacement can vary radically.
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replying to Sherman, Marc Belanger wrote: The lawn mower is probably losing spark. It will get good spark if it is cold, but once hot, one of 3 things could be happening. First, the spark plug could be filled with crud, and when it is cold, the crud has a lot of non conductive grease in there. This will turn to a liquid when hot and become conductive enough to short out the coil pack and kill the spark. I would replace it if it looks like there is crud between the edge of the steel and the porcelain on the inside of the spark plug. Look between the metal electrode and follow the porcelain where you can't see it anymore.. Yeah, thats the place, either clean it out and get the bl;ack stuff out, eliminating the short and it will probably work again. if not, the spark plug wire may be cracked and work while cold, but once it warms up, the break is separated enough not to work. Same thing with the coil. Or, the coil could be hust loose. It needs a ground to work and if the coil is loose, when cold it may be connected electrically then when it warms up it may disconnect. The coil and spark plug wire are one piece on a tecumseh or briggs and stratton and are less than 25 bucks normally. Get one, screw it on, wire it and rreplace the spark plug. Then, check to be sure the shut off wire isn't shorted to metal anywhere, it it is, the mower will still not start. tape it or reconnect it correctly to fix. The coil is under the crankcase cover. Oh, btw, the coil needs to be mounted the correct distance from the flywheel if you never seen one before. Try to line up or mark the old one before loosening it. Some coild only mount in one location so this may not matter.
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On Fri, 24 Jun 2016 20:44:02 +0000, Marc Belanger

Less than 1 chance in 10,000,000 of THAT being the problem. Spark plugs and infewrnal combustion engines don't quite work that way.

Again you are picking at straws - with something perhaps in the nieghborhood of a 1 in 5,000,000 chance.

Now you are gettind somewhere close to the realm of possibility - and even probability. The coils have solid state components in them that can fail from heat and vibration. The FIRST thing to do is remove the shroud and blow all the chaff and weed seeds out of the cooling fins to make sure the engine is cooling..Re assemble the engine - run it 'till it quits, pull the plug wire and hold the end of the wire while someone gives the rope a quick pull. If your eyes don't light up, you KNOW it is a spark problem.

Generally, if the coil is loose it will hit the flywheel and it is more likely to have a problem starting cold than hot.

Why not check that first, and quite possibly save yourself 25 bucks??

And in many cases (all older tecumsehs ) under the flywheel too.

On a Briggs (external mounted coil) a peice of cigarette package cardboard or a business card is "close enough for government work".
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Don't people look at the dates of postings?????????????????????????????
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On 06/24/2016 02:53 PM, snipped-for-privacy@att.net wrote:

Some do, some don't. Why?
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On Thursday, June 30, 2016 at 11:38:48 AM UTC-4, Red wrote:

Geeeze,
the guy has been through 2 new mowers and maybe even a new wife by now.
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