[SOLVED] Lawnmower gets hot and quits Solved

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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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...

Your wife mows? Get her this:

you didnt say if it is push or rider and engine you have,that would narrow things down

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...

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.

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

minutes

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

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.

Oh yeah-check the vent on the gas cap, too. Do the simple things first...

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?

message

valves. Grind

together.

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..

Or the seat and the valve face wear. In that case, seat and valve regrind or replacement....

Have you tried cleaning or replacing the air filter?

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

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.

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

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.....