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Riding Mower won't restart when hot

Posted by NewAtMowerRepair none (My Page) on
Fri, Jun 17, 11 at 8:10

Hi.

My riding mower (Murray 387002x92A 16 years old) will start easily and run until it runs out of gas as long as you don't stop mid-mow. If you stop, it has to cool down 30 or 45 minutes before you can restart it.

On a hot engine, the flywheel has trouble spinning. I think the starter gear goes up and engages with the flywheel teeth but isn't strong enough to turn it.

Here's what I've done recently as a tune-up and also as an attempt to fix the problem:

1) New air filter
2) New spark plug
3) New magneto
4) New oil
5) New battery
6) Sea Foam carb cleaner added to gas
7) New muffler (old was falling apart)
8) New gas cap (old was falling apart)
9) Verified a blue spark on cold engine and hot engine
10) Replaced fuel shut-off valve. This mower doesn't typically have one, but the previous owner had installed one, which was leaking.

Any ideas? I'm certainly no mower repair guy, though I've learned a lot though this experience. I really appreciate any advice you guys can give me.

Thanks.
Steve.


Follow-Up Postings:

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RE: Riding Mower won't restart when hot

Just a correction. I realized on the way to work this morning that number 9 doesn't make sense. Sorry-- I was typing faster than I was thinking this morning. Blue spark on a cold engine, not on a hot engine since the flywheel is not turning.

Thanks.
Steve.


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RE: Riding Mower won't restart when hot

IF it's a Briggs OHV engine, a valve adjustment may allow the compression release to function properly.


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RE: Riding Mower won't restart when hot

Thank you, Bill.

My engine is a 12hp Briggs vertical shaft engine 282700
http://www.hammerwall.com/Manuals/Briggs & Stratton/Description/28A700/Briggs and Stratton Engine Manual/272697/

Is this an OHV engine?

I'm a pretty handy guy with no small engine experience except for what I mentioned in my first post. Is a valve adjustment something I could likely handle myself? How much of the engine has to come apart?

Also, I'm curious about the physics. Why would the valve have trouble on a hot engine and not a cold engine? Is it because some metal is expanding and things just don't seat right when it gets hot?

Thank you so much for your help!

Steve.


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RE: Riding Mower won't restart when hot

I have seen engines do this exact thing when the valve gap clearance between tappet and stem is too close. this was on a regular valve engine. for those you have to remove head and valve cover and the valves need to come out. a valve spring compressor is needed. it also requires the carb to have to come off too. reset to spec for your engine. that info can be found on the b&s internet site or from a service manual that can be found at your local library.would reccomend have some one experienced help you.


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RE: Riding Mower won't restart when hot

  • Posted by baymee LehighValleyPA (My Page) on
    Sat, Jun 18, 11 at 19:01

I had this problem on my Kohler cast iron 12HP. I properly adjusted the valves and nothing changed. The flywheel will turn around and just stop like hitting a brick wall, and then it will barely go past that point and start.

Been like that for years.


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RE: Riding Mower won't restart when hot

" If you stop, it has to cool down 30 or 45 minutes before you can restart it. On a hot engine, the flywheel has trouble spinning. I think the starter gear goes up and engages with the flywheel teeth but isn't strong enough to turn it."

"I have seen engines do this exact thing when the valve gap clearance between tappet and stem is too close"

These two statements do not go together. On a B&S engine, the closer the valve gap is the easier it cranks. WIDE valve gap lessens the compression release effectiveness, closer gap improves compression release thus easier turning.

Walt Conner


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RE: Riding Mower won't restart when hot

baymee you appear to be describing a timing issue which will cause that.


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RE: Riding Mower won't restart when hot

Wow, thanks everybody. Seems like we don't have consensus, and a valve adjustment seems like a job I would pay for, so it's worth waiting for more ideas. Besides, being early in the mowing season, I don't want my mower out of commission if the repair goes wrong or gets delayed. I'm better off just taking a long break to let it cool if I need to stop early.

That being said, I was really hoping you all would suggest something easier and cheaper. I was rooting for the solenoid. Any chance of that being the problem? (Starter was my second guess-- maybe easy but not cheap.)

Anyhow, please keep the ideas coming and continue the discussion if there's anything to add. This is really helpful.

Thank you!
Steve.


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RE: Riding Mower won't restart when hot

A Briggs 28Axxx is NOT an OHV engine, so the valve adj. idea doesn't apply.

IF you have a volt meter, you can do voltage drop tests to isolate that part of the system that is causing the problem.

To do so, you basically put the + lead on the battery + side of the component and the - lead "downstream" toward the battery - terminal.

WHILE CRANKING, you read the voltage indicated.
Ideally, there would be ZERO V drop.
More than a couple 1/10ths per component is too much.

You can isolate everything down to things such as the battery cable itself to the terminal on the end of the battery cable.

My guess is a "tired" starter motor. Worn bushings & brushes can reduce performance considerably.


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RE: Riding Mower won't restart when hot

Hi, Bill. Thank you! That sounds like fun. I might do that someday when my wife can help me (she can sit in the driver's seat) and I can check voltages.


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RE: Riding Mower won't restart when hot

A couple of observations. I don't get your model # to come up in Briggs look up, and the Murray # doesn't seem to be of any help either. It would be helpful to post the model and type # to know for sure. If the cylinder head looks as the one in the picture, then no problem. The Hammerwall link is showing a different model #. If this is an aftermarket fuel cap, they sometimes like to put the part # sticker over the vent hole in the cap- like MTD likes to do. I don't see any indication that the cooling system has been cleaned. If this is a significant oil burner, bad carbon build up in the combustion chamber doesn't help. With all this being said, Bill's probably right with the starter being tired, but it would be good to know the answers to these questions.


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RE: Riding Mower won't restart when hot

Thanks, tomplum!

I apologize for posting imprecise engine model information before. I did a quick web search when I should have just gone to the mower and gotten the information:

model 282707
type 0122-01
code 9509084D

Here is the correct link:
http://www.briggsandstratton.com/engines/support/?NTT=282707-0122-01

No stickers on fuel cap.
No problem with burning oil.
I'm sure the cooling system was probably never cleaned. What does the cooling system consist of? The big heat sink where the spark plug screws in is free of debris. Anything else I should do in this regard?

Thank you again and again!
Steve.


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RE: Riding Mower won't restart when hot

aha,

i bought a toro ride on mower from GardenSkill lawn mower range. my mower would stop when getting too hot. changing oil did the trick. i have to say, the people i bought it from were helpful. perhaps it is worth speaking to the same company and see if they would offer adivce without having to have bought from them!

Here is a link that might be useful: Ride on Mower


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RE: Riding Mower won't restart when hot

Hi, salih.

What a nice idea. I'd feel a bit guilty calling them since they did not sell me the mower, but it's worth a try if the other ideas don't work.

Thank you so much for this suggestion.

Steve.


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RE: Riding Mower won't restart when hot

My yard bug with a 9 horse b and s does the same thing....I'm gonna try and Chang the oil....


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RE: Riding Mower won't restart when hot

So...another thread that leaves us hanging becuase the original poster never followed up. I have read SO many of these on the net. I was reading to learn and just curious. Oil change curing hot restart. I have to really think about that one. So....anyone ever find out what the true problem was and maybe the solution to it?


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RE: Riding Mower won't restart when hot

Homegrown55, I'm very sorry for not following-up.

The problem has not been solved. I never checked the voltage drop on the starter, but I agree that the starter is most likely "tired". Not worth the price of a new one, so I won't bother testing it. I just know that if I stop mid-mow, I need to let it cool down 30 minutes before starting it back up. No worries.

Have a great day.

Steve.


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