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Discussion Starter #1 (Edited)
I have a 2009 Sportsman 500 HO I bought new. I have taken it to Colorado the last 4 years, the first year it ran fine, but the last 3 it has not. The problem is when I am in a hard pull in low gear it acts like it is running out of gas. To get it to run I had to pull the vent hose from the gas tank and blow some air pressure into the tank. Sometimes there would be gas dripping out of the hose. I went to the Polaris dealer in Gunnison,CO and they said you might put another line off of the one and put one of them up high enough so no gas would come out and the other down lower so gas can come out the lower hose. The ATV IS NOT fuel injected and besides the smaller jet (147.50) the only thing I've done is put a UNI air filter on it. Does anybody have any suggestions ??? I'm going back out there this fall and ride and I would like to not have any problems. I can ride it like that but it's a pain !!
 

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it sounds like the fuel is boiling and getting into the vent and creating negative pressure in the tank. aka vapor lock. this is more common in the twin cylinders but happens in the value lines. the solution is to put a better insulating material on the bottom of the fuel tank.

this is what I used to replace the foil tape that was coming undone on my bike. http://www.summitracing.com/parts/dei-010412/overview/
 

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Welcome to the board!
 

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it sounds like the fuel is boiling and getting into the vent and creating negative pressure in the tank. aka vapor lock. this is more common in the twin cylinders but happens in the value lines. the solution is to put a better insulating material on the bottom of the fuel tank.

this is what I used to replace the foil tape that was coming undone on my bike. http://www.summitracing.com/parts/dei-010412/overview/
Yep, need to insulate the tank and use alcohol free fuel. It is available in Gunnison. Also, with the Uni filter you might need to go back to a larger jet to help it run cooler.
 

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Discussion Starter #5 (Edited)
I'll put some more insulation on the tank. What size jet do you recommend ? I don't want to go to much, there are times we ride over 13,000 ft. It runs fine except for the problem mentioned. The bad part about trying anything is I won't know it works until I get there. It's hard to simulate that kind of condition in Missouri !! Thanks !!
 

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It does sound like Vapor Locking that has been around as long as there have been carbs.

Did you ever try the factor size jet up there? Did it run too rich?
 

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Discussion Starter #7
Polaris recommends a 147.5. It runs fine. Around 11,700 or so you can smell a little gas if you are going slower, other than that it's fine, except for the lose of power.
 

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Looks like 155 is stock. I'd try about a 150 or 152. You're gonna loose power above 10,000 ft. no matter what you do. There just isn't as much oxygen up there. My Honda riding buddies run stock jetting out there without any problems although they are a little rich. Another guy in our crew ran his 04 Sportsman with stock jets also and did OK.
I think the best bet for you is the extra insulation and good quality fuel. You could also try a little hotter plug to prevent fouling. Some folks change the clutch springs and fly weights to help at high altitude. Even my 800 EFI bogs some going up American flag mtn. but good fuel and extra insulation does help. I also learned to let the machine run till the fan kicks off after a hard climb to help keep the fuel cooler.
When are you going back out to the high country? We plan to be there around the middle to the end of July this year. Look us up and we'll fry a big mess of trout or something.
 

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polman500 that is a good idea to let the engine temp drop back down to the normal range where no fan assist is required. In summer temps does this take several minutes of idle time?
 

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Discussion Starter #10
Headed out August 23rd. Going to stay in Pitkin for a week. Will take the gas tank off and put on some more insulation so I can do a better job putting it on. More of a job that way but I think it will be worth the effort though. Can't hardly wait !!!
 

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Headed out August 23rd. Going to stay in Pitkin for a week. Will take the gas tank off and put on some more insulation so I can do a better job putting it on. More of a job that way but I think it will be worth the effort though. Can't hardly wait !!!
Yeah, taking the tank off is the only way to cover it well. On our first trip to Taylor, I was having fuel boiling issues and failure to restart after hard climbs above tree line. It got so bad on top of Hancock Pass that fuel erupted like a volcano when I removed the tank lid...NOT FUN! I ended up having to pour some cool fuel out of the Rotopax into the tank to get restarted. You could actually hear it and look down in the tank and watch it boil like a tea kettle.
I used this stuff http://www.summitracing.com/parts/hsp-721202/overview/ to insulate the entire tank bottom and all the fuel lines and even did the air box too. I also put a double layer on the part of the tank right above the exhaust pipe. I sealed the edges of the mat with foil tape used for HVAC ducting. That treatment along with using good quality alcohol-free fuel eliminated the problem.
If you get a chance, you should take a day and go over to Crested Butte and ride across Paradise Divide to Schofield Pass and down by the Devil's Punch Bowl (not for the faint of heart). Circle around Lead King Basin and back up by Crystal Mill. It's a long hard 40+ miles and pretty rough in places but well worth the effort. Some of the most beautiful scenery in Colorado in my opinion.
 

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I am new here, I just bought a 2004union 500 sportsman ho and it is leaking fuel out the overflow tube. Could use some suggestions.
under what circumstances and conditions does this happen?
 

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I am new here, I just bought a 2004union 500 sportsman ho and it is leaking fuel out the overflow tube. Could use some suggestions.
You just need a good cleaning and/or a float valve. In the future, you need to start your own thread when you have a question rather than hijack someone else's. You will get more answers to YOUR questions that way.
 

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Ive had good luck with wrapping main fuel line from gas valve to carp with the heat reflective tape, I bought a whole roll at home depo several years ago, looks like duct tape only shiney..I live in Wyo at about a mile high, we run a 152.5 main in the 500 HO,s
 

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Discussion Starter #20
I have a 152.5 jet I may try that. Got it all insulated also did the gas lines, now just waiting for August 23rd to try it out !!!
 
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