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I have a 04-05 Polaris sportsman 500 H.O that has been giving me some problems.
To start, I'll give some background on what I've done so far:
Carbs have been cleaned and carb kit has been installed. Fluids have been changer regularly. Valve clearance has been set, new spark plug, clean air filter, fresh gas. My spedo quit working so it's currently unplugged.

The issue is at low rpm, from just after the atv starts to move, it sputters/patters and power loss is slightly noticeable..if I give it 1/4-3/4 throttle it will come out of it and runs like a champ.

Anybody have suggestions or similar experiences with this issue?
 

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I'd say it was carby, and that it might be an adjustment rather than a blocked jet.. Float level, idle mixture would be the two things I'd be checking.. Mixture first of course.

When you are adjusting the idle, it's important the mixture is set with the idle speed set as low as possible. You adjust the mixture till it's in the best position, if you turn it a little one way it will run rich, and a little the other way and it will run lean, set it to the center of those two points. Then adjust the speed to a low idle. Now repeat the mixture adjustment, to the center of rich/lean. Now adjust the speed again. Keep doing those two steps till it's set with as little throttle opening as possible with the mixture set to center. Finally, set the idle speed to specs.

When it's set like that the butterfly or slide will be opening and covering the two idle discharge holes as they should be, so that as the throttle opens, the idle mixture, which initially was discharging a fuel mix with extra air in it from the second or aircleaner side discharge hole, will start drawing airfuel out of both discharge holes, and it will be mixture without the leaning effect of the air being drawn it through the up stream/second hole.. It gives an automatic enrichening as you open the throttle..
 
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