I've got a 1997 Polaris sportsman that you can fire it up and it runs great for about 5 minutes. I'll be going full bore with it and all of a suddon it starts sputtering out and I slow down and it barely idles. If I give it any gas it kills. It will fire right up and run at a weak idle. If I shut it off and wait like 4 or 5 hours (or until the next day). It fires up and has good power for about 5 minutes and then the same problem over again. Is it a weak coil, fuel pump.?? I took the carb apart and cleaned it but did not put a kit in it.. Did not help... Any ideas are greatly appreciated.. Thanks guys.

 

Check that the tank vent line is open and not pinched as it goes down into the steering post hole. Can cause vapor locking condition.Also to test the fuel pump,pull the line off the carb when it dies on you and crank the engine over. Should be a steady stream of fuel from the fuel pump. On some models if the tank shielding has deteriorated or not enough air circulating, can cause gas to almost boil not allowing fuel to go through the petcock into the pump then the carb. That's a couple things to check. Another is to pull the plug and see if you have spark when it dies on you. Could be an electrical problem. There is a reverse limiter module under the front panel that can short out and cause it to limit and die in forward range also. You can pull the black wire from the limiter to see if this helps. Item #32 is the module. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse
Even a stator,cdi or coil breaking down when hot can be the problem. For that a manual that shows the stator,pick up coil and ignition coil resistance checks can help. Here's a link to a service manual.http://gh-ftp.com/ORV%20Manuals/Pola...e%20Manual.pdf
Plus you can't over rule another common problem on 1996-2000 Sportsman 500s and that is exhaust cam lobe wear. Usually if it wears down it will just idle and die under throttle,but best while you're checking things out to give it a look also.Her's one posters pics of what his looked like.http://forums.atvconnection.com/pola...d-cam-pic.html
Hopefully this is enough to help you track down the problem.

 

Thanks.. I was looking at the cam problem and I don't think that's it because the problem comes and goes and it never backfires. The shields on it are all busted up and ziptied together, maybe that's something to look at. I think I will look at the vent tube and check the fuel pump operation when it idles weak.. Should the fuel spray out under pressure or just come out in a steady stream?? Thank you

 

Should be a pulsating stream of fuel as the engine turns over. Every machine is a little different,but if the stream is weak or just dribbles when it dies on you,then it could be a fuel pump. Cheaper to replace one than to rebuild it. Eliminate this and move on the next thing if fuel supply isn't the problem.

 

I'll check it out, Thanks.

 

A quick way to find out it a gas venting problem is to run it with gas cap off. If it runs good then that means the tank in not breathing through vent line well.

 

I'll try that too. I let it sit all winter in Minnesota with the batt. in it though and now I can't get enough charge in it to even crank over. Even after it was on trickle charge all night. Time for a batt. I guess...

 

Pull start it or boost start it off your car.