I bought this 1999 sportsman 500 to fix up and sell. It had been sitting for at least a year or two do to a stator problem. Got that all fixed and cleaned everything up( new spark plug, new air filter, change fluids, ect.). She fired right up and idles great but when you hit the gas it boggs down to the point of dying. Its also just about blows the airbox cover off when you hit the gas. Ive found a similar post on here but no one was able to come to a conclusion. The entire airbox assembly is correct and tight with no leaks or cracks. It reads about 130 psi at the cylinder head, and seems to be getting sufficiant gas. I pulled the carb off and re adjusted the fuel needle to factory (2 5/8 out) and cleaned it. Ive worked on my share of polaris atv's but this ones got me. Any ideas are greatly appreciated.

Thanks, Jason

 

Check the exhaust cam lobe for for damage, ground down? Popping back through air box an indication of that,also intake boot ok,not cracked?

 

Ill check the cam today, the intake boot is fine

 

So.... Pulled the cam today and it aint good fellas! The center lobe assumingly the exhaust lobe is not only worn but its literally almost a perfect circle. The intake lobes are good and meet usable specs. What a Joke! How is this possible on an atv with only 2500 miles on it. I cant justify a new one on this thing so guess I'm lookin for a used one that will work.

 

<div class="FTQUOTE"><begin quote>Originally posted by: hesborn2fly

So.... Pulled the cam today and it aint good fellas! The center lobe assumingly the exhaust lobe is not only worn but its literally almost a perfect circle. The intake lobes are good and meet usable specs. What a Joke! How is this possible on an atv with only 2500 miles on it. I cant justify a new one on this thing so guess I'm lookin for a used one that will work.</end quote></div>

Happens all the time! I'd say 95% of the ones I've found ground down are from infrequent oil changes,WRONG oil and filter! When you replace cam be sure to clean screen on tank as probably will be full of shavings! Good luck

 

By the way I put a new flywheel on and cant remember what the the old ones timing marks looked like. Is the "T" mark for TDC or is it the three lines just beside the "T" mark that indicates TDC on the flywheel? The book just states " line up the mark in the timing window" it doesnt say which one it is.

Thanks

 

the "T" is for tdc,then the cam index pin with sprocket lines up center of the head.

 

Where can you buy a replacement cam? I have not been able to locate a new or used one.

 

my local polaris dealer had one in stock, but I got one on ebay for 195.00 brand new factory polaris, finding a used one is next to impossible in good condition. Any way you go its expensive.

 

Does anyone have any tips on getting this timed perfectly. I dont have the new cam yet but just reading through my manual I see many ways to screw this up.