Kan Kicking Kohler ZT740

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  #1  
Old 05-11-18, 06:33 PM
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Kan Kicking Kohler ZT740

Spec # is 1312...?

Kind of a beast of an engine on a Bad Boy 2015 elite 60" fab. Pro series Kohler 747cc.

333 hours on it in three years so hard commercial use.

Gent said he started it up about half throttle, it started he throttled up and it quit, would not restart.
I hit the carb with some prime and not even a pop. Pull the plugs, got spark on both sides. Try a bit of prime in the cylinder, not even a hiccup.

Out comes the compression gauge and I get 120 PSI on both cylinders. Plugs are wet, fuel smells good, only thing left should be timing...? Inspect the shear key just cuz, and perfectly intact.

Pull the valve covers and check all. Both both valves on both sides moving full and clearance is about .005. Valve overlap is good.

So time to call the smart guy after some more hiny and noggin scratchin. Give him the run down and he agrees, he is stumped as well. Bit of concern about compression since he says this engine has no compression release. He likes to see 170-180, but agrees it should hiccup or belch or sumin.

So he suggests a leak down:
90% blow by on the right, 80% blow by from the left. Air is escaping into the crank case, no sound from carb or exhaust.
I just assume rings are the problem but when I call the tech back, he is not convinced that is all.

Even rings for this thing are pricy, 70 or so per set and gasket kit another 50. With labor figure 700 if I find nothing else and the rings cure it.

Replacement engine is 1200 + freight and 1 hr labor, 1 year warranty since it is commercial use.

I have had twin briggs with similar symptoms that were brand new but had set out in the yard in crates for 3 years, then some monkey goes and uses a can of starter fluid on it to keep it running in hopes of it cleaning itself up...and rings cured a couple....
But advised the customer for a new engine since he does use it for a living. Should be in Tuesday.

Just curious if any thing someone else might know, the tech and I plan to keep in touch and sleep on this one......
 
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Old 05-11-18, 07:51 PM
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Are the plugs firing? Have you removed plugs and checked them for spark?
Think a new set of plugs might be in order here.

RR
 
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Old 05-11-18, 09:54 PM
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Yes tried new plugs and in fact used an HEi Spark tester on both sides and nice great blue spark.

Pull the plugs, got spark on both sides
 
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Old 05-12-18, 01:11 AM
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I don't see how rings on both cylinders went from running to not even a pop or sign of starting in just one instant. Especially in 333 hours. Check head gaskets I suppose. Maybe something got sucked into the intake and poked holes in the pistons? Had that happen a time or two on the older kohler commands. Screws from the butterfly valve in the carb.
 
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Old 05-12-18, 07:11 AM
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I would go back to a flooded engine. Shut off the gas to the carb, pull plugs, spin it over to flush out the fuel vapors. Then hand feed a little gas into the plug hole and see if you get anything.
 
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Old 05-12-18, 10:25 AM
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I don't understand either. Head gasket should show on leak down.
Plugs were wet as in no spark or no compression cylinders are not flooded...nothing expels when cranking.

Some further info/confession from the customer. (Always take the first given symptoms with a grain of salt, customers will not out right admit to any error on their part) :
Now confesses that the engine was buried in dirt, grass etc. and got very hot. First told me had changed the oil and cleaned spark plugs, when putting the plugs back in claims one hole was plugged with dirt...???

I am starting to think he ran it overheated, shut down for however long and when would not restart decided to do some preventative maintenance.

I was going to pull the heads and have a look and likely will when time allows, but he has opted to go with new engine so, I will have the core for a winter project.
 
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Old 05-12-18, 12:04 PM
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I might add that his preventative maintenance would have covered any signs of what might have been wrong IE: The plugs were cleaned, With a file no less :facepalm: the oil was changed etc.
 
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