Kohler CV18S Sudden Smoking

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  #1  
Old 08-20-06, 10:13 PM
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Kohler CV18S Sudden Smoking

Hi,

I have a Scotts lawn tractor with the Kohler Command,18 HP,vertical shaft engine. The tractor is 9 years old but only has 150 hrs. on it. It has been meticulously maintained....for example, synthetic oil has always been used, upon starting,the engine is allowed to warm up at low rpm for a few minutes,the engine is throttled down slowly to prevent backfires and allowed to idle a few minutes to cool before shutting down. Now the problem: I went to cut the lawn today and started it and blue/white smoke filled the shed. It was fine the previous cutting. The engine runs fine with the smoking except for a slight miss at idle presumably from oil fouling. The smoking is very significant. At mid rpm,each plug wire was removed to verify each cylinder was firing. They both were. Smoke puffed OUT of the oil filler indicating positive crankcase pressure. Inspection of the plugs revealed normal burn in one cylinder,and an oil fouling in the other. The fouling cylinder is the one with the oil separator on the valve cover. I understand there are breather reed valves for each cylinder. Now the questions.....
1. If there was a breather problem,wouldn't it affect both cylinders?
2. If there was a faulty reed valve on the offending cylinder,wouldn't compression be bad? (I haven't checked compression yet,but I assume it must be decent by the plug wire removal test).
3. If it was a valve seal,why would the crankcase be pressurized?
4. I can't imagine a ring problem because of the suddenness and low hours unless a catastophic breakage,but then again,the cylinder makes power.

Just looking for some ideas before I dive into this and my time right now is precious. Thanks in advance.
 
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  #2  
Old 08-20-06, 11:44 PM
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I would suspect a blown head gasket, but you need to perform a leakdown test on the cylinders to narrow down the problem. Is the oil level tto full? Does the oil smell like gas?
 
  #3  
Old 08-21-06, 12:14 AM
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Hi Cheese,

Thanks for the reply. I'll look into the head gasket. I guess I just couldn't believe that could be possible because of the low hours but.......now that you've got me thinking about it,total run time may be low,however,total heating and cooling cycles must be in the hundreds because it doesn't take long to mow the grass. Twenty minutes to cut the lawn with 150 hrs. total run time = 450 heat/cool cycles,and its the heat/cool cycles that is rough on head gaskets. Even though the head and block are both aluminum and the expansion should be close to uniform,I guess it's still alot. I'll lock up the crank and put 50 psi into the cylinder and see what kind of leakage I get like you also suggest. By the way,oil level is fine(It's been running with this level all season),and as far as gas smell in the case,I'll check into that.
Once again,thanks for the reply and good ideas.
LeeLee
 
  #4  
Old 08-21-06, 12:51 PM
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Diagnosis Complete

Hi Cheese,

Excellent call Cheese. I performed the leakdown test and it failed miserably. Air could be heard escaping into the case. I disassembled and the head gasket has a nice clean path eroded in it from the oil passage to the chamber. I ordered the parts to do both cylinders. There is a new part # for the head gaskets. Hopefully they are improved with a scrub plate. The old one is graphite on both sides. I ordered new head bolts also because I think they may be TTY. Thanks again for the info.

LeeLee
 
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