--------------------------------------------------------------------------------

Any one that has had their Polaris ATV pull oil into the airbox under extended heavy throttle use (climbing or tracks) may appreciate this easy fix.

I attached a vacuum gauge to the airbox and it confirmed my suspicion that while the engine was under load, quite a low pressure area is created in the box.

I also measured a positive pressure in the crankcase through the breather hose that is connected to the airbox. This causes oil that is being thrown around in the engine while lubricating, to be drawn through the breather hose and into the low pressure area in the airbox making one "H" of a mess.

Solution? Disconnect the breather hose at the airbox and tie strap it to the choke or throttle cable. I put a small piece of foam in the hose to keep bugs out. Plug the inlet into the airbox in any manner that suits you.
Silicone, wood, or duct tape - your choice. Not plugging the airbox inlet could effect your carb tuning, depending on your mod's.

Took it for a test ride. Airbox dry and clean as a whistle and Quad performs as it did before.

Hope this is helpfull !!

 

isnt that relief hose alos used to expel any condesation into the airbox?

 

im not 100 % sure but i dont know as if i would not want to run the breath hose in the air box as its there for a vent the crank and fumes, but if it works i would just find out for sure if it was me.

 

Yes, you're both right. The hose into the airbox serves as a positive crankcase ventilation system, a poor mans emission control, but we had real good engine and performance life before pcv systems came out in the 70's. The concern about condensation is valid but when you take the hose off at the air box and run the engine you'll see what I mean when I say " the pressure pulses from the engine will evacuate any moisture (condensation) when its running. There is quite a definite pulse comes out of the hose". Take the hose off the airbox and you'll see what I mean. It's a 2 minute job.

 

Not to start an arguement...But the p.c.v. system creates negative pressure in the crankcase, very useful in saving horse power loss when you're out bouncing around on the trails. The churning and sloshing oil builds pressure in the crankcase,thus the moving parts have to fight this pressure. Pulling it out is more effective than letting it build until it finds its' way out of a tube. My .02 . . .

 

That's the value of these forums. We get to exchange ideas and opinion without getting dumped on and we all learn something. So keep the 2 cents coming, they're welcomed.

 

IMHO I would say keep the hose on the airbox. Yes it will pull a vacuum on the crankcase "making" horsepower lol. If it's pulling oil into the airbox I might guess there is too much oil in the system. The only time I have had oil in my airbox, I was on the back rack and I'm ALWAYS on the throttle. But this is only my little opinion.

 

I'm inclined to believe Polaris expects oil in the airbox and that is probably the reason for a sump and drain in it. Even with the oil level 1/2 way between the safe marks on the dip it pulls a bit of oil under sustained load.

 

you can extend the hoses into the air box further and put those little push in air filters on the ends you would still benefit from the factory setup and the oil would be stopped by the filter, and sucked back down into the engine when you back off the throttle well at least in theory it should work fine.. I am putting them on mine to keep dirty and sand out of the motor looks like a very easy place to pull contaminates into the oil.. AKA dirt water or sand.. My 2 cents spent..

 

i had this problem on my 500 last year and i just changed teh oil and filter and it when away after a lil riding maby some thick clooged stuff in the oil lines or oil filter. i havn't had a prob since.