New to the ATV thing. Following this thread and I have a question. I bought a 98 sportman 500. It runs out great then sputters and dies in about 200 yards. It will start back up but protests some. If I choke it it will start. Any easy ideas? I'm considering putting a new carb on it since I have almost no history on it.

 

First pull the fuel line from the carb and see if you have a good steady stream of fuel from the pump when you crank the engine over. If it's not then the pump could be the problem or a stopped up fuel filter. Plenty of cheap pumps on ebay.Fuel Pump For Polaris Sportsman 400 500 600 Magnum 325 Outlaw 450 Predator ATV | eBay Plus plastic fuel valves themselves can clog up over time and restrict fuel flow. Don't but a cheap Chinese carb. Rebuild this better quality Mikuni carb with a good carb kit if need be.http://www.ebay.com/itm/Polaris-Spor...5X0ZGh&vxp=mtr
I still wouldn't over look the cam/valve clearance on this model as it had problems on grinding down the exhaust lobe. Here's an example from a Scrambler 500. Bad Cam Pic - ATVConnection.com ATV Enthusiast Community
Beyond all of this it could be an electrical problem. Eliminate one thing at a time.

 

Need more info. What have you done to it? Some things to try,fresh gas, check fuel filter and air filter.
Clean carb: The BST-40 Bible | Adventure Rider

Check etc on throttle: Do some easier elimination before throwing money at new carb. here is a service manual i found to check things out too for 96 thru 98 models
https://www.thequadconnection.com/Ma...e%20Manual.pdf

 

He has the older BST 34 carb on the 98 not the later BST 40 HO carb on the 2001 Sportsman.

 

Thanks guys. My son suggested the small screen in the carb intake. I'll start with the simple things first.

 

Make sure you check fuel supply to the carb from the fuel pump.Plenty of these that wear out over time or get dirt clogged.

 

i'm looking for a little help, I have a 2002 500 sportsman bought new in 2003, ran great unit late 2004 with only 900 miles on it, it had all the same symptoms as a bad cam kinda idles backfires when you give it any gas. it has been sitting ever since, i have now started to look into it in December 2016 ( been busy) so ive been following this thread and have followed what every one has been checking, cam is good, exhaust rocker has a small groove from the decompression ball, compression test (cold) 120 psi, leak down test was 40% lose also cold loosing through the crank breather tube. Any ideas? Need piston and rings? any info will help

 

I guess you checked/adjusted valves when you checked the cam.This could be a lot of the problem if you didn't. 40% leakage if accurate is way too much. You can hear this amount of leakage either through the exhaust pipe(valves) or through the crank case vent if piston/ring problems. Possibly air hiss may come from both areas.Might be time to tear the head and cylinder off.Check valve leakage with solvent in the intake and exhaust ports along with checking rings and piston wear against cylinder.2002 had the HO cam and usually not a problem like the earlier cams.Normal compression ranged from 55 psi to about 90psi,some would show higher. 900 miles isn't anything on a 500,but sound like you have a problem somewhere.

 

Thanks, sounds like piston/rings, i forgot to mention when it started running poorly it had oil in the air box, i guess just like the leak down getting past the rings. strange it has such good compression.

 

Been using good oil?