Polaris ATV blowing white smoke

Discussion in 'The Garage' started by btcn, Jun 28, 2013.

  1. btcn

    btcn Long timer

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    Hello, so I'm working on a Polaris Sportsman 300 4X4, it runs ok and starts real easy but it blows white smoke like crazy, I mean it'll fog up the whole damn neighborhood. Its also an air cooled engine, so that means its burning oil I believe.

    So I ran a compression test, it was about 155-160 PSI cold, and warm I believe it'd be maybe a few PSI more? I believe that is pretty good compression for it right? I thought it'd be more like 120 or less and be rings or something.

    So what do you believe could cause this? Diesel in the fuel? Pre mix? That is a slight possibility as it is not mine [yet!], but its very unlikely. I will flush out the tank anyways just to be sure. So what would cause white smoke with good compression and air cooled, IF it has clean gas?:huh

    Also, just for reference, I'll tell you what I was told when this happened. So this is a ranch quad, it was used to pull manure trailers up a steep dirt road everyday [30 horses shit!], and twice a day pulling a trailer with a heavy load of hay for the horses all over the place. And the guy just floored the shit out of it going up the hill every day, and being aircooled and only 300 cc, and especially on wet days, its possibly pulling between 600 and 1,400 lbs+ rider weight, up a very steep grade to the manure pile. NOt good I'd Imagine. Now they use a Honda 450, I still think a 600 or so would be more suitable. But one day, the lady was driving it and it just started smoking like that, I believe, it wasn't a gradual thing. Its only a couple years old too I believe. It's been sitting about 1 year now.

    Oh, also, when I pulled the plug to do a compression test, it was very wet and oily so it is got to be some oil? And when I shut her down, the muffler smokes a tiny bit of white smoke for a couple minutes when its warm, almost like the muffler is burning it's own small bit of oil.

    Any ideas? I appreciate any help or ideas.
    #1
  2. concours

    concours WFO for 44 years

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    It's a 2-stroke. Oil pump cable may be stuck, inspect it. What oil is in there?
    #2
  3. btcn

    btcn Long timer

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    I'm pretty sure it's a 4 stroke motor.
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  4. concours

    concours WFO for 44 years

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    What year? Did the guy at least use LOW RANGE for pulling? My bad, I thought 335 was as weenie as the 4 stroke Sporties went. How many hours/miles?
    #4
  5. gatorgrizz27

    gatorgrizz27 Been here awhile

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    Valve seals are bad, not a big deal to replace them even without pulling the head. Pull the valve cover, use the rope/ compressed air trick in the spark plug hole to keep from dropping the valve, compress the retainers (most annoying part) with a pry bar or make a tool, remove keepers, springs, and seals, pop new ones on and good to go.
    #5
  6. concours

    concours WFO for 44 years

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    Broken oil control ring would do that.
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  7. Switchblade315

    Switchblade315 Long timer

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    I second the broke oil ring idea, valve seals tend to go slow and smaoke when cold and slack off as they warm up. A oil ring will just smoke like mad all the time and it doesn't cause a compression drop when it goes.
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  8. btcn

    btcn Long timer

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    Ok it sounds a lot like an oil control ring then. Its probly not valves then because Engine temp has nothing to do with the smoke, from the second you start it up to full temp it smokes like hell, and it has compression.

    So how hard would it be to do a ring job? I know how to get into the motor, I have worked around engines a lot but never really gotten that deep into them. With the shop manual I'm sure I could figure it out.

    And thanks concours and Switchblade315.

    I'll probably check the very basic things like flush the fuel out and check the air filter just to make sure, and if not then start the rebuild.
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  9. concours

    concours WFO for 44 years

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    Get the FACTORY shop manual from the dealer, the Clymer/Haynes stuff is shit. Properly CLEANING before disassembly will be a challenge, take the plastic/tank off before washing thoroughly. Good luck! Keep us posted
    #9
  10. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

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    If it is smoking that much you may be getting a false compression reading caused by too much carbon in the cylinder head, but you'll find out one way or another when everything comes apart.
    #10
  11. btcn

    btcn Long timer

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    Yea I believe the owners have the factor manual, I'll find out for sure that'd be pretty helpful.

    And you mean cleaning the engine off before disassembly?

    I'll be sure to keep y'all up to date.
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  12. btcn

    btcn Long timer

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    Yea that could be true too. Yea I'm sure I'll find out when I pull it apart and I'll take pics too.
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  13. concours

    concours WFO for 44 years

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    Yes, the mud/dirt caked all over the frame/wiring etc. that is above the engine must be cleaned well.
    #13
  14. Switchblade315

    Switchblade315 Long timer

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    also even once you do the rebuild if you don't clean the head pipe and muffler out it will still smoke until all the old oil burns out so don't let that scare you. my experience with those quads is the worst part is getting the motor off, you might get lucky and be able to slide the top end off with it still in the frame. and get a good factory manual, even if you find one on the net somewhere in a pdf.
    #14
  15. btcn

    btcn Long timer

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    concours I see what your saying now.

    Switchblade315 yea that makes sense I can see the muffler is pretty oily. Yea it looks like it'll be a PITA to get it out, but I'll try and get the manual soon.
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  16. concours

    concours WFO for 44 years

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    Your compression test reveals good compression, so this may not apply to you. The common failure mode to air cooled ATV's is MUD CAKED CYLINDER and then the cooling ceases, rapid piston/ring/bore wear/excessive oil consumption quickly follow. Suzuki Quadsport/runner 230 were easily ruined.
    #16
  17. Switchblade315

    Switchblade315 Long timer

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    it will burn out over time, but you can wash it out with any solvent and leave it to dry a few days, it will help.
    #17
  18. concours

    concours WFO for 44 years

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    Here in the rusty North, we call it rustproofing:lol3
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  19. btcn

    btcn Long timer

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    So yestarday I tore the engine apart. I downloaded the manual and it was pretty helpful. Ran into a couple pain in the asses like the cam bolt being extremely tight and trying to find a 12 point socket the right size for the head bolts [I haven't seen bolts like that before], and then loosening them without stripping due to extreme tightness, but I just never gave up and got it all off.

    So, the compression rings look good I think, and the oil ring doesn't look broken or anything obvious. I don't know if its worn or not, I will take a pic and post it later and see what y'all think. I think the piston looks ok, and the cylinder appears to be ok with maybe a little scratching. There is a good amount of carbon buildup on the valve head though.

    So I'm thinking maybe get the cylinder honed, and replace the rings? I'll post pics so y'all can tell me what the rings look like.

    The manual says compression should be 120-140 or so I believe, so it has perfect, and I can feel the compression when I pulled the pull starter rope. So it HAS to be the oil ring right? Not valve seals due to constant smoking?
    #19
  20. btcn

    btcn Long timer

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    So any ideas how to tell if the oil rings are bad? I will post a pic ASAP when I get back to my garage. I do notice the oil ring is not as wide as the compression rings, but they are not damaged and appear to be in ok shape looks wise. I also took off one of the oil rings and tried to put it in the cylinder, it fits but not very tight. Could this be the cause of the problem?

    I also notice there is scratching on the piston and cylinder where the intake valve is, I can feel it with my finger nails a little. But if this was my problem wouldn't I have lost compression?
    #20