Ok, I am new to this forum but I have used it a lot to get help. I cannot seem to find help for this anywhere else.

I have a 2001 Polaris Expedition 425

The first time I noticed a problem was when I was riding the ATV and it wouldn't accelerate. By that I mean that when I hit the throttle, it would "putter" at a certain RPM and wouldn't rev anymore. I later on noticed that there was a very steady stream of gas dripping from my airbox.

I took off the cover and the entire air filter was swollen with gasoline; it was drenched. I did some examining and realized that fuel was coming from two places:

1.) The carburetor - it was slowly dripping back into the air box (through the air filter hole). Also, on this machine the carb is roughly level with the airbox, so its not like it was getting sucked up into the airbox from there.

and 2.) a hose from the airbox to the "Cam Shaft Cover" (pics below). What I noticed from this is that it seems to happen most when it is warmed up, and when the engine is revving down after a high rev. This is where a SIGNIFICANT amount of gasoline was coming from. At times, it would literally spray from this line.

I figured it was a very simple diagnosis: There is excess fuel in places where it should not be, Therefor the carb in some way or another is giving too much gas.

Ok so at this point I thought I had the problem identified, so I tried to solve it.

First of all: a few months ago, I cleaned the carb in and out.

So anyways, I took the carb apart cleaned it and did a lot of research and asking. It sounded like a lot of people agreed that it was the needle valve AND/OR a simple adjustment that needed to be made to the carb.

Sure enough, I took apart the carb, looked at the needle valve, and the tip of it was broken off and clogging the opening. Perfect, I thought I had found the problem, so I ordered the new valve and seat, put it in, got everything back together and it ran a little better, but lo and behold, the same symptoms occurred.

So, with the new seat and needle valve in there I figured, after some more asking and research, that the carb just needed to be adjusted because too much gas was still getting in the engine.

I tried my hand at adjusting the carb two times, with no positive results. So, since I was confident that the adjustment was all that needed to be made, I accepted my lack of expertise and precision tools, and brought it into the shop.

$200 dollars later, the machine runs great. The shop cleaned a clogged pilot, adjusted the float, adjusted the air/fuel mixture screw, and replaced the needle valve and seat (which I just replaced a week ago, so thats odd but I didn't think much of it because the machine ran good). It idled like it never did before and I thought the problem was solved. I took it for a ride and, in less than ten minutes, the same symptoms started showing up again. Though, they were way less severe this time.

I called the shop back and they said they could take a look at it again for free, since that was the problem I brought it in to be fixed.

I am completely stuck, I have no idea whats going on.

Any help will be much appreciated. Thank you.

P.S. I attached a parts diagram of the camshaft cover - part number 34. The hose went from that to the airbox with a filter on it along the way.

 

The crank case vapor and pressure are vented through the cam shaft cover to the air box. If gas was coming from it the engine oil is contaminated. If no one has changed the oil and filter,or even if they have,you still possibly may have washed the rings down with gas or have excessive cam and rocker arm wear. First thing I'd do is check the oil to see if it's gas contaminated,pull the valve cover and look at the cam lobes. Takes a lot of gas over a period of time to contaminate 5 1/2 quarts of oil,but can happen and can do some serious damage if it has.

 

Thank you for the reply, I checked the oil cap and sure enough, the fluid came shooting out. It was overflowing. And yes, it was a combination of oil and gas, As I could smell the gas in the oil. What does this mean? could it be a broken valve? Broken Piston Ring?

 

I'd check the cam first for any wear on the lobes and rocker arm pads. You can pull the rocker block off if necessary as a unit to inspect closer. Compression test is kinda hard to tell on these because of the decompression device on the cam ,but on average they're supposed to have between 55-90 psi if engine is in good shape. If any lower than 40 psi I'd suspect ring/piston damage. If it runs good until it warms up then starts acting up,possible rings could be loosing seal against cylinder walls. I'm just looking at worst case on this,hopefully you don't have to tear it down.

 

Ok, The shop is currently taking a look at it again for free. But I'll check out the cam when I get a chance. It does seem like it spits out gas and looses acceleration capabilities when it is warmed up.

What kind of damage could have happened from the engine running while excess gas and oil mixture in where only oil should be? I haven't ran it hard or long at all since i have noticed these problems.

 

Like I mentioned,pistons and rings can get washed down and cams can wear down from thinned out oil,but may not be the case if you caught it quick enough. Hopefully the shop can find out what the problem is and again hopefully it's nothing major. Keep us updated as to what they find.

 

Ok, so I got it back from the shop and they explained that when the needle was broken before, gas kept leaking with nothing to stop it. Therefor, because it had no where to go, it leaked downing the crank case. They changed the oil and said that it was common when the carb malfunctioned like that that the fuel would leak down in the crank case.

So at this point I should have no problems ideally and everything should be running well. So far it almost seems this way.

It may be that I am paranoid and in denial about the problem being fixed at this point.

So I took it out and did some pretty heavy plowing with it. I kept a paper towel scrunched up right next to the hole where the gas/oil mixture was shooting into the airbox before. I did this to: protect the air filter from getting soaked again, and to check to see if anything was coming from the tube.

After a long time running the machine and plowing, I looked at and felt the paper towel. It had moisture on it from the hole, But only a tiny bit. It looked clean (not gas or oil colored). I smelled it and it smelled like fresh oil.

I then checked the oil and smelled it. I feel like this is where my paranoia comes in, I think I might smell a tiny trace of gas in the oil. (Is it possible this tiny trace would just be from the residue of the old contaminated oil?)


The machine runs great. But I feel like I might be paranoid.

So my question now is: Is it normal for a small amount of moisture to come through that tube? or is none at all supposed to?

 

One more thing I just thought of is that it might be possible that the moisture that ended up on the paper towel was also residue inside of the tube and filter (on the hose). Maybe?

 

Good that you'd be paranoid as I would be too on something like this,but probably it's a little left over gas residue as you mentioned. Especially if the oil was only changed once. Usually when this happens on gas or water contamination of the oil, people throw a couple quarts cheap oil and a cheap filter for the first change,run it a few minutes and change to the good stuff. Since your machine holds 5 1/2 quarts I can see why they probably didn't.. Just my two cents on this is on the next oil change make it a little sooner than you normally would change the oil and filter. Then go back to your regular schedule. One thing that a lot of people over look when rebuilding carbs is the float arm and pin. Doesn't come in any kits(dealer items)and they can wear just as much as the float needle itself. If you start to notice any gas in the air box or any gas smell in the oil,this is something I'd check out quick. A worn pin will be shiny and rounded down,the inner hole of the float arm can enlarge and the float can get wobbly and in some cases stick and cause engine flooding.Hopefully you dodged a bullet on this one. Plus on this one particular Mikuni carb there is an air cap diaphragm that can wear over the years and cause problems. It needs to be inspected any time the carb is taken apart.Item #12.http://www.cyclepartswarehouse.com/f...2001&fveh=5567

 

Ok sounds good. Thank you for all of your help! I really appreciate it. As far as some fluid/moisture coming from that breather hose as I mentioned, I did some more research and it sounds like at high RPMs and high engine loads the oil can make its way up that tube a little bit as the oil gets sloshed around. What I was worried about sounds to be normal for what I was doing. I will keep a close watch on everything involved in this issue for quite a while now.