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98 arctic cat 300 2x4 hi rev choke when started


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Have a 1998 AC 300 2x4, Just installed a new carburetor. Engine starts easy but the choke RPMs are very hi and take along time (5-10 mins when cold out). After engine has warmed up choke releases and it idles and runs fine., It does no have an electric choke. The choke lever is never used and it seems like an auto choke? Long story short, how can I lower the choke rpm levels?

 

Also, carb came with a spare145 jet, not 100% sure what is installed. Could this impact choke RPMs?

 

 

Any help and information greatly appreciated.

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The way you are describing it sounds like an automatic choke, if you never move the choke lever you are not choking it manually , unless its automatic and as it warms up the choke turns off. Is it an aftermarket ot OEM carb. Not sure about the jet 145 seems large for a 300. Whats is installed in it now. 

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I'd warm it up and adjust the idle mixture and speed first, then see if it still does it after it's cooled off.

It might be too rich at idle when warm, and so have the speed wound up. Then when it's cold the rich mixture is just right and the wound in idle speed screw makes it race. Could be....

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Yes it is an aftermarket, and yes one would think it has an automatic choke the way it acts. I will have to double check on the jet sizing. I think idle mixture is where iI am going next. And of course it most inaccessible without loosening it up and spinning the carb.. for access. thanks for the input all.

 

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My expieience with most after markets is they are factory set a little lean, but Mech is right it is acting rich, my thoughts is try to adjust the mixture as well, and see if it helps, but lean running will also make it idle faster, but it should idle faster all the time not just when its cold.

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Idle adjusts down easily, it was low when first installed so raised it. Once it settles down from the cold start high idle it runs fine. But I will say when I hit the throttle, it does blow some black making me think lean. I ordered a tool mentioned about and will see if adjusting it clears the problem. tool supposed to be here monday. will follow up then

 

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What ever it is, it's always best to try adjusting the mixture first because that is (even the hard to get at adjusters),  the easiest thing to try.

It checks the mixture screw is changing the mixture enough too, which is a good thing to check. If winding the screw a full turn each way didn't have a dramatic effect, then it would be a guide/helpful in the diagnosis.

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  • 2 weeks later...

I've recently (in the past few days) been through the wringer with these Chinese clone carbs.  I ordered a Motoku that is suppose to be a direct replacement for my QR250 (same basic engine as the Arctic Cat) and it came all sorts of wrong. Came with a  #40 pilot jet (factory spec is #15), an unlabelled main, and a just barely oversize needle jet (120).  I replcaed the pilot and main with genuine mikuni jets, they are cheap after all. I then fought with the pilot screw. I also have one of the fancy 90* screwdrivers but for some reason it flat out does not work, it just gets caught in the housing. And I have one of the expensive motion pro ones.  After fighting continuous flooding and rich running I pulled the bowl back off and found that the float level was set way, way too high. It was at 12.5mm, factory spec is 17.1mm.  Fixed that and it runs a whole lot better now. These CV carbs are a right pain in the butt, they are so sensitive.  I'm still not convinced the needle itself is on the right slot, but still workng on it...

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I know i kind of went through the same with my Eiger, PO drilled out the jets and it was on an aftermarket and he drilled them too large and i dint want to fool with that carb anymore, so i bought a used Kei Hin off Ebay and rebuilt it with an all Balls carb kit and its working good. Looking back if i was to do it again i would buy OEM parts to rebuild it with.

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