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Discussion Starter #1
Hi there looking for some opinions here. I have a 98 sportsman 500 I think I'm having carb issues. I rebuilt top end 3 months ago and ran good through break in it smelt like it was on the rich side. I just recently put new jets and new needle and seat in because after it warms up the low end gets boggy then clears up with higher rpm. The air screw is at 3 turns out also. The dealership said to put jets and needle and seat in and it should be fixed but it is still running the same they also said it's not the can .Anyone else have any ideas?
 

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I would start by completely disassembling the entire carburetor and cleaning out every passage with carb cleaner and compressed air. Just changing the jet may not be enough. The pilot jet and associated passageways in the carb are very small and need to be properly cleaned.

There isn’t air-screw on these CV carburetors, there is a pilot air jet under the slide diaphragm that meters air flow at idle it should be a 160. If you are talking about the small screw on the front bottom side of the carburetor it is called the pilot screw and it adjusts fuel flow on the low end. 3 turns out is too much fuel (rich) try 2 turns out which is the factory setting and then adjust from there while it’s running for optimum idle. It takes a really short screw driver to accomplish this.

Other things to check:
Improperly adjusted enricher (choke)
Float level out of adjustment should be 13mm from float bowl mating surface
The rubber diaphragm on the top of the slide for cracks.
What slot is the e-clip on the jet-needle at if it’s adjustable, is the plastic spacer still under the e-clip?
Did you get the right jets? Factory setting (0-3000 ft elevation) should be a 142.5 main, 42.5 pilot. If they sold you a pilot jet for a non-CV carb it won’t work right either, there is a difference.
The ignition system could also cause the symptoms you feel, weak spark, bad plug wire, do you have the right plug, NGK BKR5ES 0.028 gap.
Lastly check the fuel pump. It is a diaphragm operated pump off engine vacuum. If the diaphragm in the pump goes bad it sucks fuel directly into the engine. At higher RPM the engine may be able to deal with it but a low speed it may be too much.

That’s all I can think of for now. Good luck.
 

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Discussion Starter #4
So I took the carb off re adjusted the choke and turned the screw to 2 turns out and seems tobe running worse although it will just sit and idle without killing now I ran it around for aawhile and was running great but after the fan kicked on it won't get much past half throttle and acts like it is getting to much fuel And now it won't clear up at all.. this thing is really starting to frustrate me. I really don't want to bring it in because I don't have the money for a shop to deal with it right now. Does it sound like the cam at all to anyone? I was told though that if it was the cam you know right away. Mines not back firing though just being very sluggish.
 

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Discussion Starter #5
I also played with that screw and the more I turned it in the better it ran but I eventually ended up with it all the way in and it was running.a lot better but still a little hesitant. I also noticed that the float bowl drain screw was wet so that's possibly leaking would that maybe be part of the issue if it has a small leak?
 

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This doesn't make sense. First you screwed it in and it got worse but the further you screw it in the better it got? If it is screwed in all the way to run you still have issues.

A tiny leak in the float bowl will be compensated for by the needle valve letting in fuel just as it does when you burn fuel with it running. You need to fix the leak however.

The cam is easy to check. First clean the area around the valve cover so you don’t drop dirt into your engine. Remove the valve cover and spark plug and pull the engine over by hand and watch the lobes on the cam, they should be shiny smooth and not flat. All the valves should move up and down similarly. The exhaust valve lobe was the one I mostly saw fail probably due to the extra heat. Your statement about it clearing up at higher RPM makes me think the cam is fine though.

So what makes you think it is running too rich? Have you read the plug? When you screwed in the pilot screw in to 2 turns you leaned it out from the original 3 turn setting making it run even worse which tells me it was already lean to begin with.

I have seen far too many of these run bad due to a lean condition and they acts like you describe. Boggy on the low end. You can diagnose a lean condition if you have a properly adjusted choke (enricher). At the same time you blip the throttle open flip the choke lever to half. If it is lean it will rev up better due to the extra fuel you fed it through the enricher circuit. The ‘choke’ really isn’t a choke because it doesn’t block airflow. It is an enricher because it lifts a plunger allowing extra fuel to flow into the motor. If flipping the ‘choke’ lever makes it rev better you have a lean condition. This all depends on a properly adjusted ‘choke’.

If you confirm a lean condition the next thing you should do is remove the carb and take out the pilot jet. Assuming the pilot jet is new you need to prove the passageways are open in the pilot circuit of the carb body. Stick the hose of your carb cleaner into the pilot jet hole and hold open the throttle plate in the bore of the carb. Look into the bore (with safety glasses) as you spry the carb clean into the pilot jet hole. Near the front of the bore where the bottom of the throttle plate rests when closed you should see 2 separate jets of carb cleaner squirt out close to each other. If not you’ll be lean and you have some cleaning to do.

If the passageways are open you need to look for an air leak somewhere. Some reason that you are getting more air to the motor than fuel. Check the rubber carb mount for cracks. Check the diaphragm at the top of the carb slide under the brass cover. Maybe there’s a vacuum leak on the impulse line going to the fuel pump?

A trip to the dealer may be your best option at this point. All we are doing is guessing at possible causes based on the info you provide us, which isn’t making sense. Yes it may be spendy but if you’ve ruled out all the causes we’ve suggested it may be your best hope, some problems are too complex to fix online.
 

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Discussion Starter #7
Ok sorry I missed typed on one of my previous posts. But over the weekend I took the carb completely off torn completely down and cleaned everything with carb cleaner and and air hose. I also installed new throttle and enriching cables because the old ones were cracked and falling apart. I feel as if I have made some good head way it will start without having to hold the throttle open. And the enrichener also works as it should now. The only thing it's doing now is when you shut it off and turn it right back on it won't fire right up. But if you let it sit for a minute it starts right up. Seems kind of minor as to what I was dealing with though.
 

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Discussion Starter #8
So with all that now I have another issue to address all my u joints are bad on my wheeler and I have never done u joints before. Is it worth doing my self or would the axles on eBay be a better way to go?
 

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Sounds like the enricher was your problem all along. Probably stuck open and adding to much fuel all the time. U-joints are not that expensive and pretty easy to do. Cheaper than a whole new axle, and just as much work to remove and reinstall.
 

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Discussion Starter #10
I'm sure the enrichener plunger wasn't moving the way it should. No matter where I had the cable adjusted it just wouldn't run right. Do I need any special tools for u joints? I've watched YouTube videos and it doesn't seem to bad but the dealer was telling me I could mess up the axles if I do it myself but I'm sure that's how they scare people into taking it to them. But I found axle sets for my wheeler on eBay and it would run about $500 for all 4 but if I did it myself I'd spend about $240. So just trying to justify what's best to do at this point. After that I shouldn't need anything else for along Tim's besides and out change every year. Thanks for the info though guys I appreciate it.
 
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