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Discussion Starter #1
Hey guys, I have a Polaris Sportsman 90 Two-Stroke, no idea what year it is. The only indication of the year I could find is on the front under the "headlight" (which is only a reflector, this has no lights) it says "Made for yadda yadda company blah blah Taiwan Date: x/x/200"

Anyway, the issue is it starts up and idles fine...usually starts on the first kick (also has electric but kick seems to be more effective). As soon as you go past 1/4 throttle or so...it chokes down and won't run right, it even stalls if you don't let off.

Now, my thinking was the carb was full of crap so I ran some seafoam through the gas and the intake - no change. It smokes to high heaven when it runs - blue smoke (before & after seafoam)

I cannot seem to find any information regarding the mixture settings so I can only assume it has none? If it does, I'd really like to know where they are and how to adjust them.

Any information is helpful. I tried searching (google) all kinds of different combinations of words but to no avail.

Thanks!
 

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Discussion Starter #2
I should also mention that, while I haven't removed the carb yet, it does seem to be free of any funk or soot or anything like that. I should also add that this model mixes its own fuel. The closest thing I could find was the carb exploded parts view for a 2004 but...it's SLIGHTLY different.
 

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Discussion Starter #3
Pictures are worth a thousand words I guess:



I don't see any needles except what appears to be the idle adjustment.
 

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Carb Teardown

Sounds like a carb teardown is in order. The jets and passages in these small carbs are really tiny, and easily plugged. I'd bet disassembling the carb and cleaning out all of the passages with compressed air will solve your problem. I have over 30 years experience with bikes and quads, including time as a factory trained mechanic for several dealerships. Just pay attention to where everything goes when you take it apart - taking pictures as you go helps if you are a newbie. Let us know how you make out, or if you have any questions.
 

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Discussion Starter #6
What's the best way to remove the throttle linkage from the carb? Like, is there a way to do it without it being a P.I.T.A. to put back? Other than that I'd have no problem working on the carb.

Also, would I need to buy new gaskets or anything like that or...pretty much just put it back together as-is?
 

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Just unscrew the two or three screws holding the top on the carb where the cable goes in. The carb's slide will slide right out the top with no problem, and stay all together as 1 assembly. When reinstalling it the only thing you have to watch is lining up the slot that runs down the side of the slide with the little guide sticking out of the inside of the carb. Look down through the top of the carb after you pull the slide out and you will see it. If your choke is cable operated you can just unscrew it from the carb also, usualy a 12mm wrench. It will also stay together as an assembly.

Normally you can remove the float bowl without damaging the gasket. After you remove the screws from the bottom of the carb for the float bowl, tap the bowl lightly with the handle of your screwdriver. They will normally seperate pretty easily that way. Then pull the bowl off slowly, taking care not to tear the gasket. That should be the only gasket - everything else is O-rings. They only need to be replaced if they have gotten hard, or have a rip or tear. With the bowl off you can remove the float and float needle. Then remove the main jet in the middle. There should also be a small pilot jet that removes with a small straight blade screwdriver. Careful with that one not to strip the head-they are soft brass.

There is probably also an idle mixture screw on the outside of the carb body, in addition to the idle speed screw on the side. Count the number of turns in on the mixture screw so you can put it back to the same adjustment. Usually they will be in the range of 1-1/4 - 1-3/4 turns out. After everything is removed spray every hole you can find with carb cleaner then blow them all out with compressed air. Same for the main jet and pilot jet you removed earlier. Make sure all of the little holes are clear in the pilot, in addition to the hole down the middle. Resist the temptation to stick a piece of wire thru the hole.

Reassemble and enjoy! Hope this helps
 

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Discussion Starter #8




Here you mean? Those two screws circled in red? Can I take those off while the carb is still on the motor? I don't wanna get it in a way where I can't get it back on without disassembling the entire vehicle.

Also, I don't think there's any choke....there's only one cable going to the carb and that's the throttle. Others include two wires, one stiff rubber tube, and one fuel line. That's it.
 

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Yes, those are the screws for the cap/slide assembly. Yes, they can be removed with the carb still on the motor. You can loosen the clamps and rotate the carb some to make them easier to get to if need be. You have an electric choke - thats the two wires going to the carb. Just unplug the wires.
 

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Discussion Starter #10
Alright man, I think I'll tackle that today. Question though...I found a screw that's obviously for mixture adjustment, it's here indicated by the square selection - it's right behind that tube:



I adjusted that and it seemed to run better but smoked like hell. Then, without me changing the setting, it went back to not running at all except at idle and the smoke stopped. So...no idea what that means. The question marked "hole" in the carb is where there appears to be some threads but no screw. I looked in there with a flashlight and it's bright shiny metal indicating that there may have been a screw there at one point but now it's gone? Is it possible one of the mixture adjustment (if it has two?? probably does) screws fell out of the carb? Probably the high end mix adjustment? That would probably explain these issues?


I really appreciate your help! Been really good!
 

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I did a little research, and it looks like your sportsman is possibly a 2001 model. Here is a link to a parts schematic for it, including the carburetor.

http://www.bikebandit.com/houseofmo...90-a01fa09ca-2001-carburetor/o/m5562sch310390

The idle mixture screw should be on the same side as the idle adjustment, and it looks like your top square is the correct location. The bottom square looks to be an just an unused boss. There definately are not two mixture adjustment screws. The only two external adjustments will be the idle mixture and idle speed. The idle mixture will only have an affect at idle thru 1/3 throttle or less. After that it will have no affect on the running above about 1/3 throttle. Go ahead and jump in there and get that carb cleaned out and I think you will be suprised how easy it was, and will more than likely fix your problem. You can refer to the diagram I supplied the link to for help, and just post again if you have any more questions or need help. I'll be online until about 3:00pm Central, and then from about 6:00pm on. I work in Information Technology now, so it seems like I'm in front of a computer every minute I'm not in the garage or riding!
 

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Discussion Starter #12
Well, I took it all apart like you said, cleaned it thoroughly, and no change occurred. All of the jets were clean - spotless in fact. It still won't run past 1/4 throttle. Idles all day long but as soon as you try to open it up it conks out. Backfires are common.

I don't know what to do now. It's getting plenty of fuel, the spark plug is brand new. Fuel is good, mixture is good. I tried it with the choke plugged in and with it not...didn't make any difference either.
 

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Discussion Starter #13
I'm still stuck with this...I have no idea what to do now. I have no idea what the hell could be wrong with it!
 

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Im sorting out some carb issues with mine too, it's exactly the same as yours. Remember there is an emulsifiation tube behind the main jet that may have some crap behind it. You have to unscrew the main jet from the bottom of the carb stem, then use a small punch through the hole where you removed the slide barrel to knock the emulsification tube. You can blast that area all out. Use a torch tip cleaner and make sure there is no fuel varnish buildup in the jet. Just right next the the main jet stem there is another small pilot jet. Make sure that's clear. In the bowl itself there is a couple passageways that must be clear.

Also while the fuel line is disconnected, turn on the fuel valve and make sure you have a decent fuel flow to the carb. If it just barely dribbles then you might have some crap in the fuel filter or in the fuel tank outlet. If it has a nice steady stream then fuel supply is not the problem.


Mine is acting a bit different than yours though. Mine idles fine, and runs at 1/2 to full throttle fine, but bogs down at part throttle, only if you roll into the throttle. If you gun it, it doesnt hesitate it just leaps off.
 

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Discussion Starter #15
Yeah, I took it apart as much as possible, cleaned everything, etc. Didn't make any difference.

I ended up just replacing the carb and now it runs fine. There was no buildup anywhere in it. I don't know, there's no telling now.
 

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Yeah, I took it apart as much as possible, cleaned everything, etc. Didn't make any difference.

I ended up just replacing the carb and now it runs fine. There was no buildup anywhere in it. I don't know, there's no telling now.
Ha thats one way to fix a carb!! Sometimes crap gets built up in the passageways that's really hard to get clean. I got lucky with mine as we have a hot water pressure washer at work, and I've learned that it works amazing to clean up really cankered up nasty green varnished carbs. I can dump a whole can of carb spray through one and not get it as clean as 180*F high pressure water. Even still sometimes we end up having to replace a carb because there are so many passageways that just wont clear out.

Glad you got it sorted out though it sucks having a toy that doesnt work.
 

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I have the same problem with a 2003 sportsman 90 two stroke. I have replaced everything and it still will not rev. I changed the stator, reeds and intake, coil, spark plug, cdi, carb, and check the exhaust for blockage and nada. Still won't rev. Help!
 
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