Go BottomNew rings for a kohler engine
 | AnnBrush
Join Date: Mar 2004 Posts: 463 Troy OH 
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2007-02-28 140077
I was doing annual maintenance on my Craftsman riding mower and aside from the fact that the rest of the unit is falling apart - the engine has been really great. It's a 18hp Kohler magnum 2 cyl gas engine - model MV18S. I looked into the air filter set-up on top of the carb and noticed a lot of oil present - there was never any oil there before. I am assuming this is solid evidence of blow-by and an indicaton that one (or both) sets of cylinder rings need to be replaced. Is this correct, and if so what is involved if I chose to do it by myself. Have any of you ever done this type of thing your selves? Many thanks and cheers, Ann
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada 
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2007-02-28 140078
Ann, I wouldn't get the wrenches out just yet.
I've found that a very dirty air cleaner element will cause the same thing. Is it posible it got dirtier than it has in the past?
I would borrow a compression tester and give it a go first.
I have torn down more than my fair share of small engines, it's not too hard to do.
On the other hand, after your statement "...aside from the fact that the rest of the unit is falling apart..." are you sure you wouldn't just rather take this as an excuse to justify it's replacement with a new mower?
Best of luck. ....
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 | JAZAK5
Join Date: Jul 2003 Posts: 276 coxsackie,ny
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2007-02-28 140083
I'd run a compression test and take a look at the crankcase check valve, if there is even a little particle holding this valve open it will pull oil into the carb.This valve maintains a vacume in the crankcase so oil does not leak past the seals. ....
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 | harvey
Join Date: Sep 2000 Posts: 1550 Moravia, NY 
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2007-02-28 140084
Rings are not complicated. Typically new rings hone cylinder to break the glaze and you are set.
As Murf and Jazak said do a "DRY" check first then a "WET" check of compression. The difference "I THINK" should not be more than 20%.
To add to what they also said, did it by chance get run over full of oil?
Harvey ....
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 | yooperpete
Join Date: Jan 2004 Posts: 1413 Northern Michigan
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2007-02-28 140085
As Harvey has said, overfull has that same indication.
Another one is if you mow on uneven ground perpendicular to the slope (i.e. the tip or tilt factor). I do that allot and most of my Kohler 17 and 18's have blow by - all 6 of them matter of fact. It is not that bad to be a problem. Also if the gas is too rich and all doesn't combust, it washes down the cylinder walls, causing it to be overfull. I get that in winter months from the carb icing up. ....
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| AnnBrush
Join Date: Mar 2004 Posts: 463 Troy OH
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2007-03-01 140104
OK thanks guys - all positive comments, I'll check the compression. The air filter element is newish < 1yr of VERY light use. There is some use on slopes ±30° (cos it just fits along an embankment next to the road frontage) and the oil has never been over-filled. I will also tune the carb as it drifts a little each year and at the end of the season is always backfiring once you turn the engine off (pre-ignition?). ....
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