Dies after 30 minutes

GoRoush

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Have a 18.5 hp twin and starts up good. Seems to run real good. But after 30-40 minutes if mowing it dies and won't restart til it's good and cooled down. I have changed the coil and plugs. All good gas and nothing looks dirty don't no alot about carb adjustment or anything. Any help is appreciated. Pretty handy on diy just need to know what I'm looking for and tips on making sure all adjustments are correct
 

bertsmobile1

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An in line red spark tester would have cost 1/3 of what you have just wasted on the coil you did not need .
So now we have only the fuel system to think about.
The most common cause of these symptoms is semi-floating debris in the fuel tank forming a plug choking off the fuel supply.
When the flow stops it floats away only to be sucked back once the engine starts running again.
Easy way to confirm this by using an alternative fuel tank the instant the mower stops
If it starts fine and runs till the alternative tank is dry then time to clean your tank.
Softened fuel lines can do the same thing
 

GoRoush

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It is getting fuel all the time. After it dies. I have pulled off air cleaner and cranked on it. It is pumping plenty of fuel to it from what I can tell. Even smells of gas when trying to restart
 

bertsmobile1

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This is why I use the spark tester.
SO you could be having a valve problem
You could be having a voltage drop allowing the carb solenoid to close
However till the tests are done you could be having a lot of problems.
If I wanted to write a mower maintenance manual then I could write one for my publisher and make money on it.
Thus I have no intention of doing it here for free.
So you have basically 3 options
1) do exactly what the techs ask you to do, post the results Then follow the instructions
or
2) continue to replace random parts till eventually you replace the defective part
0r
3) sit there while every body throws their "pet problem" at you.

Your mower, your money, your time , your decision
 

catbob

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Next time it quits take the gas cap off for a few seconds and try starting it again, cap might have a plugged vent causing a vaccum, never know and it doesn't cost anything either
,
 

WeldGuy

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An exhaust valve that is adjusted too tight will do that. After running a while the valve expands just enough to leak compression.
A friend's old J-D tractor did this exact same thing because an intake valve stem was varnished up and would hang the valve open when warmed up. I suggested a HEAVY dose of Marvel Mystery Oil in the fuel tank. It only stalled out a couple times after that, then cleared up and is running great now several years later.
 

fixit1ddh

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Sounds like it has a valve seat problem. & check for proper air flow. (Cooling)
 

slomo

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How do you know you are getting fuel all the time? Remove the fuel inlet hose at the carb? Good flow there?

slomo
 

GoRoush

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How do you know you are getting fuel all the time? Remove the fuel inlet hose at the carb? Good flow there?

slomo
Yes. Getting fuel is the first thing I ever checked
 

slomo

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I would triple check the spark as Bert said. Inline spark testers are cheap. Always use it later on something else.

slomo
 
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