[ty_stephenson]

Hello everybody. I have a 2010 Polaris Sportsman 500 HO that is having some issues, I have tried all the basic stuff and nothing has worked, so here I am asking for you help. The machine has less than 400 miles on the odometer and 53 hours on the clock. I don't ride it every day, but try to at least let it run every week or so. The ATV will start up and idle just fine, however when you push on the throttle it seems to bog down, lose power, and then it will backfire, sometimes even shooting sparks out of the exhaust. I have done all of the following with no luck..
-Changed spark plug
-Changed in-line fuel filter
-Changed air filter
-Ran brand new Ethanol-Free gas along with Seafoam to clear things out.
-Cleaned the carberator and checked fuel lines for plugs.

It seems like its either not getting enough spark?? or its either getting too much or not enough gas. I'm not a mechanic or anything, just trying to get the perfect balance of fuel, air and spark and something is off. Any ideas on what it could be? I took apart what I believe is the fuel pump, which was bolted onto the side of the frame with 3 hoses attached to it, one from the tank, one to the carberator and another what I believe is a vacuum hose. Everything in the pump appears to be intact, it has some springs on little things that look like suction cups, it appears that the membrane moves and allows fuel through? When I ran the machine on idle some gas was being pumped through, and then when I revved up the machine a little more came out, but I was told gas should be gushing out and it wasnt really, which makes me wonder if its not getting enough fuel and my fuel pump is bad. A couple other thoughts that I had that may or may not be applicable.

-Bad PCV valve?
-Electrical issue (I havent noticed the fan come on in quite awhile, even when the machine seems to be warm and you would expect it to come on, could that be related?).
-The ATV came from a dealer in Vegas, I am located in Salt Lake City, UT which has a substantially higher elevation.

I have had the machine for over a year now and it ran perfectly up until a few weeks ago then all of the sudden started having issues. All regular maintenance has been done.

Any ideas that you have that can help would be greatly appreciated.

 

[fhedrickjr]

Wow. I am def NOT a Polaris expert but, when this happens, what does your speedo gauge look like? This sounds very reminicent of my problem with my 08 500 EFI when the cooling system was not working properly due to the radiator being clogged with mud. I had no clue till it started losing power and started bogging and when I pushed it, it cracked out the exhaust like a high powered rifle!! Scared me and my Grandsons pretty good! I finally looked down at my speedo and it was flashing with red highlights and the word "HOT" was flashing where the digital numbers should have been. I had to limp back to the trailer and when back to base, I had to take the upper cover off the grille and thouroughly rinse the mud out of the radiator. If the radiator is not clogged from the outside..check your coolant flow.

 

[ty_stephenson]

The speedo is normal. It has the little maintenance wrench but I just need to reset it. The radiator is clean and the coolant level is good. I have not had any issues with it overheating.

 

[fhedrickjr]

Ok. That is all I have for you. Sorry I couldn't be more helpful. Let me know how it turns out!!

 

[ty_stephenson]

Thanks for your help. I'm totally baffled by this whole situation.

 

[fhedrickjr]

I did a search outside of this forum and came up with a page of links to similar issues. Maybe you can look through them and get an idea or two to pursue. Fred.

2010 sportsman 500 ho backfiring and sputtering - Bing

 

[archer]

Could be the throttle position sensor, TPS. Simple adjustment fixes problem.
Would need to hooked up with computer.

 

[Sjjr613]

Have u pulled the spark plug and looked at it. If it's back firing through the exhaust then its a indication that its running rich. Also check the free play of your throttle.

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[Sjjr613]

The jet needle could be worn and letting to much fuel through. U could try lower the needle one notch and see.

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[ty_stephenson]

Yes I pulled the spark plug a couple weeks ago and put in a brand new one. I pulled it again today and it was black as black, totally covered in what appears to be ask because you can wipe it off. It's very fouled and may need to be replaced again. I tested the spark plug outside of the engine and can see a small spark when the engine is cranked. The free play on the throttle seems ok I think. I will try to upload a picture tomorrow of the throttle assembly

 

[ty_stephenson]

*ash not ask above

 

[archer]

Yes I pulled the spark plug a couple weeks ago and put in a brand new one. I pulled it again today and it was black as black, totally covered in what appears to be ask because you can wipe it off. It's very fouled and may need to be replaced again. I tested the spark plug outside of the engine and can see a small spark when the engine is cranked. The free play on the throttle seems ok I think. I will try to upload a picture tomorrow of the throttle assembly

The symptoms sounds like the TPS. You can't fix it without a computer showing adjustment.
Some dealers like mine will fix it for next to nothing if its the problem.

 

[Russ C]

The 500 Ho doesn't have TPS It has a carb, not EFI, sounds like throttle cable out of adjustment, should only have 1/8 inch of slack at thumb throttle adjustment is in cable about 4 inches from thumb throttle Might try running some seafoam in the gas too.

 

[ty_stephenson]

Well I took the carb apart and cleaned it, the needle and spring looked good. On the very bottom of the carb there is a hose dangling there that has a Phillips head screw on the end of that. Is that the governor adjustment? I thought it was a vacuum hose. What is it? It's still having issues and running rough. I took the fuel pump apart and cleaned it as well. Everything inside there was intact and looked normal.

 

[ty_stephenson]

Is it possible I need to adjust the position on the needle? See picture

 

[Sjjr613]

If its still running rich raise it one notch. That tube u see is the idle adjustment screw. Mine broke off to so on the other side you'll see what it was attached to. You'll need needle nose pliers to adjust it now.

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[ty_stephenson]

Does anybody know what the factory setting should be for the needle adjuster? I haven't changed it at all. Does it appear to be in the "correct" spot? As a side note I live in Salt Lake City and my elevation at my house is around 4500 feet.

 

[Sjjr613]

3

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[Sjjr613]

Raise it one notch and see how it runs

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[fhedrickjr]

I found this somewhere else on this forum:
"the factory setting is usually the middle slot which also turns out to be the 3rd from either side. But if it's not then I believe they count from the top down. Meaning if your hold the needle with the taper down the top slot is one and it counts down towards the taper. "

I also agree with the others about the correct way to read the plugs. However, if it stumbles and sputters, I get it that it will be next to impossible to get it to run a WOT blast then shut it down! Good luck with that brother. Oh, one more thing, I had trouble with my 04 400 Sportsman cracking back out of the exhaust and having poor idle, then idle racing after warming up, the valves, especially the exhaust, were too tight.