Polaris Tech Tip: Oil in Airbox Fix - Page 3 - Polaris ATV Forum
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View Poll Results: Poll: For the 850 engine, have you ever had oil in your airbox?
2009 850 - Yes 29 9.09%
2009 850 - No 17 5.33%
2010 850 - Yes 55 17.24%
2010 850 - No 19 5.96%
2011 850 - Yes 136 42.63%
2011 850 - No 31 9.72%
2012 850 - Yes 10 3.13%
2012 850 - No 12 3.76%
2013 850 - Yes 5 1.57%
2013 850 - No 5 1.57%
Voters: 319. You may not vote on this poll

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post #21 of 262 (permalink) Old 03-22-2011, 11:09 AM
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oil in airbox

pulled mine apart found oil in airbox wiped clean re assembelled with grease as instructed see how it works fingers crossed have heard there is another new breather update also for pvc has notches inside to let moisture flow back into valve cover to keep from popping oil gallery plugs in freezing weather going to check with dealer to find out ???
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post #22 of 262 (permalink) Old 03-22-2011, 11:25 AM
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Could someone that works at a dealer confirm if there is a new PCV?
Would owners of a machine in warranty get a letter about getting it changed or does Polaris only do recalls during service intervals?
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post #23 of 262 (permalink) Old 03-22-2011, 02:47 PM
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yeah there a new breather, it comes with the the valve cover / labyrinth. I got it on mine, there 5 holes in the bottom, and 2 notches for the moisture. I removed the spring in the bellow, I will try if it change something thursday.

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post #24 of 262 (permalink) Old 03-22-2011, 03:46 PM
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Removed the spring? The rubber piece would just be flopping around in there why not remove it as well?
Just don't roll the machine after taking it out.

Last edited by supercoe; 03-22-2011 at 03:47 PM. Reason: spellelling
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post #25 of 262 (permalink) Old 03-22-2011, 04:03 PM
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I think I have found the problem cause and the solution

and unfortunately, it is NOT as simple as the oil laberynth, or the valve cover. I will try to explain my experience in english (I am a native speaking person, so forgive me if I am not clear enough), and from the point of view of an MD who has been forced to learn mechanics...:-/

My first advice to all of you who have the oil in the filterbox problem in a relatively new 850 XP, is to get an accurate compression reader and measure the comprssion rate in both cilinders, full throttle. If it is anything less than 200, forget about the valve cover; that is not the problem, but the symptom.

There are a number of 850's (unknown) who SEEM to have come with a problem in the cylinders' nicasil layer finish, which roughen's up against the pistons. Cylinders get scratched (I've seen several engines opened, and they looked scary), combustion messes up, piston head's get carbonized, and compression is lost.

Pressure is then passed down along the creaks between the piston-cylinder (like if you had worn-out rings), all the way down to the carter. Carter pressure build-up transmits to the valve chamber, and when it mounts, it collapses the oil laberynth inside it, and starts flowing through the breather hose. Then, it starts spitting air and oil in the air-filter chamber.

So.....if you have oil in the chamber and the cylinder pressure readings are low, forget about ONLY changing the valve cover. Today I have changed the whole cylinder / piston / crankcase (basically the whole engine aside from the rods and the crankshaft). Pressure in the cylinders skyrocketed from a puny 125 before the change, to 230 psi. Idle rpm stopped fluctuating (I used to have from 950 to 1200, the lower end being when the piston cicle receives less presure) and is now clockwork, oscillating between 1.180 and 1.200. Sound is different. Oil spitting has stopped.

IF your compression is right and you still have oil, it might be solved by just changing the valve cover. But I would rule out compression problems first.

I will be doing a 4-days mountain expedition starting this Thursday. My air-box is now clean. Keep your fingers crossed and by Monday I'll let you know how I fare (and I am going to check compression again when I come back).

This seems like a bigger problem than Polaris has aknowledged to date, and at least in my country, nobody knows why. But 9 engines have been shipped in to replace other engines in 2010 models, like mine.

Hope this helps.


Last edited by Dogoman; 03-22-2011 at 05:12 PM.
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post #26 of 262 (permalink) Old 03-23-2011, 01:14 PM
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nice info,, but it was the Laberynth on mine the first time and they replaced the whole valve cover assembly which was a new part #. This second time,, which just happened 4 weeks ago was the breather, they replaced it and it's fixed.

I don't have trouble with the idle and my machine doesnt smoke,,,"yet",,, which is an indication of bad rings,, give it time i'm sure it will,,lol

Be sure and change your fluids regularly (especially the engine oil),,, i change all mine every 500 miles,, which is about every two and a half months since i ride so much

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If there is no trail I make one...

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2008 Sportsman 400 H.O.
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post #27 of 262 (permalink) Old 03-23-2011, 02:05 PM
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My machine never smoked.

Have you measured the compression in yours? How many hours does it have?
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post #28 of 262 (permalink) Old 03-24-2011, 03:48 AM Thread Starter
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Gasoline Quality in Argentina

Your engine problem was probably due to the high sulfur content in the gas sold in Argentina. The sulfur content found in much of the world's low quality gasoline causes some Nikasil cylinders to break down over time causing costly engine failures. The sulfur in the fuel breaks up the Nikasil lining in the cylinders, thus causing a loss of compression. Once the lining is damaged, excessive bore wear of the soft, underlying alloy occurs very quickly. Some symptoms of the Nikasil problem are rough running at idle and difficult cold starting, both due to loss of compression. In severe cases, the loss of compression is so bad that the engine loses power. Oil consumption increases dramatically as oil is sucked up the side of the leaky pistons. In extreme cases, the compression decrease is so severe the engine will not start in cold weather.

The Nikasil coating process was developed by the German firm Mahle, originally for use in the Mercedes. Audi, BMW, Ferrari and Jaguar have all used Nikasil engines in their production cars. Porsche used Nikasil in their turbocharged 917 - 935 series of race cars. In racing two strokes, both Morbidelli and Rotax have had great success with Nikasil. Nikasil has been used in thousands of professional grade chainsaws, motorcycle and marine engines, and even many NASCAR Winston Cup and Formula One engines.

Nikasil has been used in high performance engines because it allows the total elimination of poor-cooling cast-iron, and it is harder and more oleophilic (oil-liking) than cast-iron. Nikasil offers superior lubrication, reduced friction, and superior wear characteristics.

Fuel Quality in Argentina

I wonder if Polaris should rethink their business strategy for exports. Exporting products with Nikasil engines to countries with high sulfur content gasoline may be costly in both repairs and to the brand.

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Last edited by Stealthepooty; 03-24-2011 at 05:47 AM. Reason: Spelling
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post #29 of 262 (permalink) Old 03-24-2011, 07:27 AM
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Wow, awesome info Stealthepooty!
Thanks for this explanation as now its starting to make sense why such a large percent of their imported wheelers had scratched cylinder walls.
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post #30 of 262 (permalink) Old 03-26-2011, 08:22 AM
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I have had my 11 850 xp for less then 30 days.. bought it new with 0 miles on it. just changed the oil and filter at 100 miles.. checked the air filter.. and have oil in the breather.. took it to the dealer today.. of course they have never heard of the issue.. the service tech ran the VIN and pulled the tech tip from polaris.. then turns to me and says "well here it is the fix, but this isnt something polaris pays for." of course my reaction was "the f*&^ they won't.. I have had this thing for less than a month and polaris knows there is a problem coming from the factory".... they are going to perform the repair.. should have it back Monday afternoon... Will keep you posted on whether they battle me on the cost of repair..

This Thread has been good info.. I appreciate everyones input.. It definately helped going in knowing the problem before the dealer could pull any shading stuff..
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