My cam went bad as they all seem to but most people say there exhaust love is the bad one. My exhaust lobe is but one of the intake lobe is also. What would cause this? Thanks in advance!!

 

Metal flying around,heat,etc.You can get the complete cam with all the rocker arms.Polaris Sportsman 500 2x4 4x4 Cam Shaft Camshaft Rocker Arm Arms 1995 2012 | eBay

 

Is it a 500 H.O. or a non-H.O.?

 

I think Polaris only sells the H.O cam now .

 

Polaris still sells the oem #3086212 cam for the 2000 and earlier Sportsman 500s and Magnum 425s. The Ho cam is #3085855,same lobe height as the older cam ,but the duration is the difference. The ones they sell on ebay? Who knows if they're really the HO version or the old std version as most places just say their cam replaces either part number..

 

OPT - when you say the duration is different; are you simply referring to how long you can expect the cam to last?

 

Duration is how long the intake valves remain open to receive a charge of fuel and also the exhaust valves to remain open to remove the burnt gasses. Longer the valve duration,the more fuel it can take in and expel.And with a larger carb,richer jetting it can produce a little more hp than a non HO cam machine. That was the main reason for going to a larger carb(BST40)) to take advantage of this.But non HO engines have run fine with just a cam swap only and reusing the smaller BST34 carb.

 

Thanks so much! I have a 99 sportsman 500 that I got last fall pretty low hours and miles for its age (approx 2125 mi / 425 hrs) and I think it has the original cam in it yet. There is some slight sputtering when I first back it out of my shed but never seems to happen if I'm go forward with it. I'm planning on opening it up to adjust the valves this week and am going to inspect the cam. I'm hoping I don't have to replace it.

Also the crank seal on the recoil side is going bad/gone bad as it's leaking some. I've discovered this kind of by accident. I removed the recoil cover last fall after purchasing it and there was quite a bit of dirty water in it (which I thought seemed oily but was told there shouldn't be oil in it), cleaned it out well and reinstalled the cover. Opened it back up this spring to replace the gasket and to my surprise there was some oil laying in the bottom of the cover (maybe a few Tbsp). Can that seal be replaced without completely splitting the case? If I leave it, how major of a concern is it? This is my first ATV so I'm learning as I go.

 

You are pushing the over ride button while in reverse? If not they will spit and sputter. The stator has to be removed to replace the seal,plus some of the oil could be just from water that's gotten in the cover over time and mixed with grease from the starter bendix. That happens a lot also. If for any reason you remove the stator plate itself,MARK it so you can have timing right and always replace the o-ring around it as it's another source of leaks along with crank seals.Plus once off it's hard to get one back on without pinching it as they will swell. Items 4 and 8.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse Plus be sure to seal up the recoil housing with some good rtv sealant plus you can also seal the rope handle to help keep water and moisture out.