Kohler dying/blowing smoke

mwkellner

Member
I have a John Deere LT150 with a Kohler Command 15hp motor. It starts fine and runs fine for about 10 minutes. it will then bog down, blow some whiteish smoke (not a whole bunch) and die in about 30 seconds. Friend said maybe valves. There is quite a bit of carbon build up on them (exhaust especially). I can"t see any other damage, they are not bent. They are tight in the guides. I will lap/grind the valve seats. I really need other suggestions of what to do while it is apart. Do y"all think it is the valves? Or something else? The cylinder wall is smooth and undamaged but I will do rings while it is apart. Give me any advice that y"all have. I know there is more knowledge here than between me and my friend. I really like this site, I just RARELY post. Read it alot though. Thanks.
 
The white smoke sounds like unburned fuel. Like weak spark or loss of spark.

Only other thing I can think of would have been the crankcase full of gas, but you would have seen that when you went to tear down.

I think there are some reed valves under the valve covers for crankcase ventilation, be sure they are OK.

Maybe what you've done will cure it, let us know when you get it back together.
 
Steve I did check the spark (when cool) and it arced to the metal frame. Is there some reason that the spark would be good enough to run for 5-10 minutes and then bog down? What would cause the spark to weaken after it gets hot? Thanks for your help, I need it.
 
David, I did not check to see if the oil was coming out of the filler cap before I took the engine apart. What would it mean if it was coming out of the oil filler cap? I will check that when I get it back together? Thanks. I need help and trying to learn at the same time.
 
What causes the carbon(?) buildup I am seeing on the exhaust valve? Is it un-burned fuel? Too much oil in the cylider? Or just normal on a mower this old? Thanks for all of your replies.
 
Before/after takeing eng apart did you check if there was oil in air filter houseing or filter element?Oil in houseing/filter could be an indication of a sticking/stuck crankcase vent valve or possibly sticking/broken ring(s)causeing excessive blow by into crankcase blowing oil out crankcase vent into air filter smothering eng.
 
Sometimes a coil will fail when it warms up, rare but it happens, a bad spark plug will do strange things too.

I could see it losing spark to one cylinder, but that shouldn't cause it to totally stop though.

Also look at the kill wire, that would stop both coils, (and they are tied together by that wire), if it's rubbed through to ground somewhere, could be making an intermittent short. To test, unplug the wires from the coils. It will run without the wire, but you'll have to choke it or pull the plug wires to kill it.

The carbon deposits on the ex valves are caused by worn worn valve guides, carbon in combustion chamber is caused by worn oil rings. Typical of a well used engine.

Correction, the reed valves are down in the block, under the heads, between the lifters. Not sure what they do, something to do with attempting to maintain negative crankcase pressure. The fuel pump works off the crankcase pulsations, could affect that, not sure though.

One more thing, those engines, I'm told, have a history of head gasket problems. Any evidence of the gasket blown toward the push rod opening? That might pressure the crankcase to the point the fuel pump wouldn't work, another maybe...
 
Joe, I do remember that there is not excessive oil in the air filter housing. Thanks for replying. I will take all suggestions.
 
I put a new spark plug (it is a single cylinder) in it after this happened the first time and nothing changed. How could I check the coil to see if it is the problem when it gets hot? Thanks so much.
 
Just have to run it until it fails and be ready to check the spark ASAP while it's still hot. An old spark plug with the electrode removed is a good test. Plug the wire on and lay it against something grounded, watch the spark.

OK, it's a single. Well that doesn't change much, still the same basics, just one of everything! LOL

Not sure if it will have the reed valve under the head, someone on here will know. It will have some type crankcase breather, be sure it's clear and intact.

Opening the oil cap running is not a good test on a single! You will get an oil geyser, no matter how healthy the engine!
 
Don't know why I didn't send you here first, but the Kohler website has a lot of information, PDF files free for the taking! Troubleshooting, tear down and specs, all in plain english! They explain it better than I can! LOL
 
Thanks alot Steve and everyone else. I think I can get back to it on Sunday. I will post back with results or maybe more questions. I will check out the Kohler web site before this weekend.
 
2444, I don't know if it has a fuel pump. I am not
even sure what it would look like. Would a fuel
pump run fine for 5-10 minutes and then start to
quit. I hope that I can get it running, but I want
to know why it quit too for my own satisfaction.
Thanks for your reply. I need all the help I can
get.
 

sounds like maybe a fuel flow problem into the carburator. Maybe a partially blocked fuel line?
 

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