New to the site. I got a 2002 sportsman 500 that has been sitting. It wouldn't idle. I cleaned carb, drained gas, and found missing clamps to carb that I fixed. Now it idles fine but when I press the throttle it boggs down and seems to be backfiring through the airbox. It will run but slow. I also noticed oil leaking from the valve cover. Any suggestions would be greatly appreciated.
Thanks everyone

 

If you just cleaned the carb and didn't install a kit,possibly could still have a problem if the needle and seat are worn,float level's off,main jet stopped up.Plus pull the fuel line from the carb and crank the engine over. Should be a steady pulse of fuel if the pump is ok.
Had several 500s come in that had one valve cover screw on the left hand side vibrate out causing them to leak and sling oil out. Plus pull the valve cover and check that intake and exhaust valve clearance is good. .006 intake and exhaust. http://www.ebay.com/itm/2001-2002-Polaris-Sportsman-500-4x4-Carburetor-Rebuild-Kit-Carb-Repair-Set-NEW-/371144129552?pt=Motors_ATV_Parts_Accessories&hash=item5669e9fc10&vxp=mtr

 

Thanks for the quick response. I'll order a kit. I adjusted the throttle and it didn't change anything so I guess it would still be in the carb.

 

I put a new kit in. Fuel pump is pumping good. Same result. Won't take half throttle before bogging down and backfiring. So I'm pretty much narrowed down to the intake and exhaust valve or lobes. Are these parts I should order before getting into this operation? Is there something else it could be? Thanks

 

Look at the cam.. If it looks similar to this one,you'll need to replace it and the exhaust rocker arm.Bad Cam Pic - ATVConnection.com ATV Enthusiast Community
Plenty after market ones on ebay now cheaper than oem that include the rocker arms, cam sprocket,gasket.http://www.ebay.com/itm/POLARIS-SPORTSMAN-500-2X4-4X4-CAMSHAFT-CAM-ROCKER-ARM-GEAR-KIT-SET-1996-2012-/261472878394?pt=Motors_ATV_Parts_Accessories&hash=item3ce0ff7f3a&vxp=mtr Plus don't overlook simple things like a split intake manifold you may have missed,dirty air filter or air box not sealed tight.
Doesn't happen very often,but if the plastic limiting nut on the drive clutch loosens and backs off,the machine will limit also because the clutch can't close all the way. Item #8 on the parts break down.http://www.cyclepartswarehouse.com/f...2002&fveh=5582

 

I took the cover and valves off. Looks like there should be 3 lobes on the camshaft. The center one is nearly worn down flush with the camshaft. Looks like my problem is found. Do you recommend buying the whole kit that you posted or just the camshaft?

 

When you take the rocker block off look at the pad on the exhaust rocker arm. Usually it's scored/damaged also. I always replaced both the cam and rocker arm. The complete aftermarket kits are $219 versus $270 just for an oem cam. You can check out ebay as to other prices,but this is the best deal I've found. Have to figure all the shavings isn't good for the intake rocker arms also. Surprising part is that it doesn't happen very often on 2001 models and later that have the HO cams,but anythings possible.

 

Thanks for all the help. I'm going to order the kit you suggested. I've got a good picture of the cam still installed but couldn't load it on here. I'll get back on here when I get it installed and let you know how it goes.

 

If it looks similar to this one I wouldn't bother on a picture.. I've seen plenty of them ground down. Bad Cam Pic - ATVConnection.com ATV Enthusiast Community

 

I changed camshaft. Didn't replace the gear. Now it won't start and backfires. Any suggestions.