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I have a 1998 Polaris Sportsman 500. I recently bought it used from a family friend for a hell of a deal. I have put all new fluids in and cleaned the bike up pretty well. For 1200 miles it is in pretty good shape. Here is the problem. Everything runs fine and I have been riding it nearly everyday. It starts up fine gears work shifts well from N to D and R. However when I am riding the fastest the bike will go is around 28-30 Mph. I am certain that this bike being a 500 has to have more power then this. It accelerates pretty slow and almost feels like it has a governer around that speed. I have checked under the throttle and cannot find any sort of physical governor however I could be wrong. A governor could not be the problem. Seems I am loosing a whole lot of power somewhere. Yesterday I was riding up a steep hill and it almost seemed as if it was struggling to climb it at full throttle. Any Ideas/ Suggestions on what I could check? I was thinking my next things to check would be fuel lines/ Carb and then air flow.
 

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First off, welcome to the board!
 

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Thanks! I appreciate it! Just was searching for a answer to my problem and figured a forum would be a great way too. Pretty neat place!
 

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you could try a fresh spark plug,clean carburetor.
the older ones had issues with soft camshafts,you may want to take the valve cover off and inspect the lobes,would be a good time to adjust the valves also. .006" on intake and exhaust and there are fourvalves
 

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So I cleaned carb replaced spark plug only to find out I have a broken fuel pump. Could that be a reason for such a power loss? Also how do you adjust those valves you were talking about?? And where can those be found.
 

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that broken fuel pump is most likely your power loss issue.
If the valves have never been adjusted,it wouldn't be a bad idea to do so.
remove plastic side covers,remove spark plug.
the top of the motor is where the valve cover is and that cover needs to be removed.there should six to eight bolts that you need to take out to get the cover off,i don't remember if the size is 3/8" or 10 mm.,anyway take the bolts out and give the cover a lil tap and it should fall off.you normally can reuse the gasket.
With the rope starter,pull slowly until you get the piston at top dead center on the compression stroke,it's hard to do but one thing that also helps is that the camshaft has a couple dots on it ,just make that those are parallel with the valve cover surface and you should be where you are supposed to be. set the gap at .006" for intake and exhaust this engine does have four valves.
 
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