i have a 2000 polaris sportsman 500 was riding it and it made a real loud popping sound around engine when checked it out the battery was out of water and the
fan was running very slowly since this happened the four wheeler idles good starts good but when you give it gas it spits and sputters backfires i have changed the stator with a new one from ricks stators on ebay and i also replaced the cdi box and the voltage regulator with used ones but i have a repair manual an have checked the parts and they test good have replaced the spark plug fuel filter and took carb off and cleaned it and reset idle screw 2 5/8 turns with all this the problem is still there an help with this 4 wheeler would be greatly appreacated thanks eric brown

 

Sounds like you've checked all around the machine,but have you checked the cam for excessive wear on the exhaust lobe?? Will exhibit the same symptoms you're describing, will crank and idle fine,but will spit and cough back through the carb when you give it a little throttle.1996-2000 were the bad years on the cam problems. Check the exhaust lobe and see if its the same as intake lobes or if it has been worn down. If lobe is elliptical and doesn't look worn then make sure valves are set at .006 intake and exhaust. OPT

 

think that was one of the years taht had bad cams that wore out as mentioned.

 

no sir i have not gotten into engine other that took head cap and side panel off to check tdc and timing those checked out ok what is the easest way to test this havent been into one of these engines

 

Remove the valve cover and inspect the big lobe in the middle of the cam shaft,should look like the intake lobes on either end of cam. If ground down,replace the cam and exhaust rocker arm. Just read your manual, replacement is not that hard. OPT

 

dear sirs i checked the valves and checked the valve clearance all is good any other suggestions thanks eric brown

 

Did you look CLOSE at the cam lobes?? OPT