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Discussion Starter #1
Hi all.
So back to it with my 1991 indy 650.
I installed new choke cable and adjusted it according to the manual. It fire up fine within 2 pulls. Machine will idle at 1500 rpm for a few seconds and then drop down to like 600 rpm. If its been running and I stop the machine I have to put the throttle up to a quarter to get it started and keep it running.
Other than this issue it runs fine through mid and top end.
This issue was the same before I replaced the choke cable. I completely disassembled the carbs in november and cleaned them in an ultrasonic cleaner. I have adjusted the idle screw and air screw is set to factory spec.
I'm at a loss.
 

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Bring the idle up to 1700-1900 as that is what it should be at least that is what all of my Polaris machines were ever set at including the ones I have right now. Also sounds like something is in one of the passage ways of the carb or jets. I don't use ultrasonic cleaners, I and most of the people here clean them by hand along with using a small piece of wire for the passages and jets. All it takes is a very small piece of something in one of the carbs to screw up the whole system. It wouldn't hurt to clean them again only by hand with the small piece of wire for the passages & jets, carb cleaner and a tooth brush. About the only thing I can think of at this point. You've done pretty much everything else but re-clean the carbs.
 

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I'm thinking the choke plungers are not hitting the bottom. The way I usually do it is to adjust them so the plunger is hitting bottom just as the threads on the cap are starting. Screw the cap on and the plunger should be pushing firmly on the hole below.

If one or all of the plungers are not hitting bottom, it will start just fine and idle fine until it gets warmed up, and then slobber on itself and not idle very well.
 

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Discussion Starter #4
Well I recleaned the carbs by hand, this wire and compressed air. Re adjusted the choke and turned in the idle screw 2.5 turns.
Machine idles at around 1900 rpm now and goes down to 1400 rpm when hot. What its doing now is it will abruptly lose spark for a split second and then fire back up. So im thinking I've got a cdi going bad or a something is grounding out somewhere.
 

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Very possible as if it is the original one it wouldn't be shocking for it to have an issue. At least it is back idling correctly now. Sounds like there was something in the carb and doing it that way you got it out. Over time the electronics inside the CDI will absorb heat and that can cause it to have an issue. I have replaced a few CDI's on my sleds in my time. Thankfully only one has had a stator go out at the same time. Also the stator might be something to look at as well. Just to make sure there isn't any wires corroded or fraying. I would start with the grounds and looking for frayed wires like you suggested and go from there before buying any parts. And if possible if someone you know has a good CDI swap it out and see if that improves it once you check for the grounds, if it does then you have your answer.
 

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Unplug your throttle safety switch and see if your problem goes away. Its possible that you have a little too much slack in your cable.
 
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