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Can anyone tell me why my exmark 48" mower with a kohler engine will not start when it gets hot? when it cools down starts fine?

Does oil look clean & on full mark? Check air filter for replacement. Remove blower housing top of engine & clean everything by hand, no water or liquids, removing all debris from engine, a small nylon brush & shop vac work well as does a piece of coat hanger wire in small spaces such as engine cooling fins on heads. Debris will cause engine to run hot & not be able to breathe fresh air properly as will a dirty air filter.

Could just be that the intake valve is too tight.

check your ignition coil. They can fail under load.

If you can see your coil without dismantling try cooling the coil (yeah , I know...how??) Anyway, we used to temp test incoming components at a company. Transistors that failed at hot would often come alive again at cold. These components were rejects and returned to the source. Your coil contains a small circuit made up of similar parts. If they are overheated they fail.

I've never tried but I wonder if he put an inline spark tester on his coil and let the mower run til it dies maybe the spark tester would give an analysis. Spark testers aren't too expensive and if you're not willing to spend a few bucks to do your own work then the dealer is the best place.

The op doesn't mention that it cuts off while mowing only that it will not start when hot. Of course we will probably never know the answer from the op.

true, true.

Mikel1 said:

The op doesn't mention that it cuts off while mowing only that it will not start when hot. Of course we will probably never know the answer from the op.

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... an' why it's likely not a coil or coils at fault.
Altough I have had experience with a B&S 20hp doing exactly as described.
Mow fine, pull up for smoko and the bugger wouldn't start until cooled completely.
A new coil gave me back my smokos on that ride

Not a whinge as such but I do wish the guys with problems gave more of a story
to the problem. Seems a bit one sided with responders putting up 200words when
an OP believes 50words tells all. I wear glasses, select a new tinfoil hat for each
post read, an' have my squeeze doing taro (cards) as a backstop.
Still carnt figure most of the pleas until well into the thread, if at all.

I am betting timing on this one. Sloppy valve lash.

KK

I remember how the temp test was done on the transistors. They would douse them with CO2 (I think) , a fire extinquisher? Anyway, it was a spray that took the parts down to cold very rapidly.

TRIVIA (what else) . Plato probe that is quite impressive has components known as "trace." Each transistor is tagged and documented from the minute it is formed in the foundry, diced into little squares, die bonded with little wires, burned in (like your tractor parts should be), temp cycled -cold hot cold etc. Finally issued a pedigree as "fit to use" and sold at a zillion times the chinese battery charger price. I know y'all needed this....:confused2:

motoman said:

I remember how the temp test was done on the transistors. They would douse them with CO2 (I think) , a fire extinquisher? Anyway, it was a spray that took the parts down to cold very rapidly.

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Freon, R11 I believe. Extra low temps can break these things.
Now what has been used since freons were banned I got no idea.

Pressure Temp Chart > Refrigerant Boiling Points

TRIVIA (what else) . Plato probe that is quite impressive has components known as "trace." Each transistor is tagged and documented from the minute it is formed in the foundry, diced into little squares, die bonded with little wires, burned in (like your tractor parts should be), temp cycled -cold hot cold etc. Finally issued a pedigree as "fit to use" and sold at a zillion times the chinese battery charger price. I know y'all needed this....:confused2:

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Ah hah...!... yer a Homeland Security mole, ' cos you left out the step where nano transmitter
is fitted to get the whole finished component (NIC) reporting back to Great Wall enabling theft
of Humvee engine monitoring software.
We know .... yer not foolin us with your trivia ;-D

/ wags finger

KK

If it will still fire the plugs when hot then check the valve lash. Kohler engines have valve problems.