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La105 Acting Up


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#1 Reverend Blair OFFLINE  

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Posted August 21, 2012 - 07:02 PM

I mowed the front today and my JD LA 105 is doing something odd. It kind of bogs down, then releases a cloud (and I mean a big cloud) of blue and white smoke. Then it clears itself and runs fine. It did this three times in about twenty minutes, then it ran without a problem for about 30 minutes.

The first time was coming up out of the ditch. The second and third times were during sharp turns. The grass is relatively short, dry, and not thick. No power steering so I doubt the turns have anything to do with it. The oil is clean, the air breathers are new, the plugs look good. Other than the ditch, the lawn is level. Same fuel as in the 420 and I've had no issues with that one even though it sees a lot more use.

Any ideas?

#2 dave8338 OFFLINE  

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Posted August 21, 2012 - 07:18 PM

My guess would be that there was excess oil in the PCV tube (or where it goes into the air cleaner assembly) and that it swallowed a gulp of oil as you were heading out of the ditch. "Usually"... excessive blow by is caused by worn compression rings.

Other than that, I'm not sure what would cause that with the possible exception of extremely worn valve stem seals.
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#3 John@Reliable OFFLINE  

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Posted August 21, 2012 - 07:39 PM

Is the oil level good? If it was blue first, then white, I would lean towards overfilled crankcase, remember when the oil gets hot it will expand, uneven ground..............
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#4 Reverend Blair OFFLINE  

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Posted August 21, 2012 - 07:44 PM

My guess would be that there was excess oil in the PCV tube (or where it goes into the air cleaner assembly) and that it swallowed a gulp of oil as you were heading out of the ditch.


Shouldn't I see some sign of oil on the air breather if it was in PCV though? It's only got about five hours on it since I changed that, and both the paper and foam filters are pristine.

"Usually"... excessive blow by is caused by worn compression rings.

Other than that, I'm not sure what would cause that with the possible exception of extremely worn valve stem seals.


This is part of my confusion...this engine has never used a drop of oil before. Usually there is some sign of wear before you get a lot of blow-by, or something breaks and it's consistent.

#5 Reverend Blair OFFLINE  

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Posted August 21, 2012 - 07:52 PM

Is the oil level good? If it was blue first, then white, I would lean towards overfilled crankcase, remember when the oil gets hot it will expand, uneven ground..............


Yeah, that's the first thing I thought of...that I'd over-filled it when I changed oil. It's just a tad below the fill line even hot though. That's about where it was after I changed oil. Also, it's done about 5 hours since then without an issue. That includes one mowing of that same ditch.

#6 dave8338 OFFLINE  

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Posted August 21, 2012 - 07:54 PM

My thought is that the slope of the ditch had more to do with the smoke, than anything else. The fact that it puffed blueish-white smoke means that the oil entered the combustion from somewhere. PCV, rings, valve stem seals, are the only means of this happening. A compression test may be in order.

Engines are very durable machines. The are designed to run and few things get in the way of that principle. Excessive heat will cause a thinning of the oil and can lead to flash off but is usually accompanied by loss of power and the dreaded "hot engine" smell.
As you mention none of these symptoms, it is my assumption that these factors are not part of the equation.

I'm thinking on this quandary...
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#7 JDBrian OFFLINE  

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Posted August 22, 2012 - 05:01 AM

The fact that the engine bogs down then releases the smoke is a clue I think. Is the engine being loaded down or is something else changing to cause the engine to stumble (fuel, or spark problem maybe) Could some of the smoke be from excessive fuel as the governor reacts to the lower engine speed? It's an odd symptom and there are some good theories here but I really can't think what else it could be other than oil pooling somewhere, perhaps in the ohv area, and then suddenly getting into the combustion chamber through a loose valve seal. It might be worth pulling the plugs to see if there is any evidence of fouling.
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#8 Reverend Blair OFFLINE  

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Posted August 22, 2012 - 05:35 AM

I have pulled the plugs, Brian. They look normal. It's like the only symptom is the smoke. All I can think of is something wacky with either fuel or oil, so I'm going to replace both today after work. I'll pick up a compression tester on the weekend.

I really hate mysteries.

#9 glgrumpy ONLINE  

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Posted August 22, 2012 - 06:31 AM

You didn't mention what engine size you have. I have L130 with Vertical shaft Kohler and it has pretty much always puffed smoke pretty good on start-up and a few minutes after when first getting out to mow. I myself belive oil collects some in those layed down cylinders while parked and then is burned off next time I start/mow with it. I mow on a hill sideways quite a bit, haven't had any issues with that. Just a thought.

#10 JDBrian OFFLINE  

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Posted August 22, 2012 - 07:59 AM

That reminds me that I had a lt160 with a Kohler 16hp single and it would also puff smoke at startup.

#11 Reverend Blair OFFLINE  

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Posted August 22, 2012 - 09:33 PM

It's the 19.5 HP Briggs. It puffs a tiny bit on start-up, always has.

I drained the oil and fuel and replaced it with fresh stuff today. Changed the oil and fuel filters. Ran it for about an hour on level ground watering trees etc., then went and drove around the ditch just to test it. No smoke.

I'm still going to test the compression on the weekend, but my guess is that something got in the fuel.




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