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Discussion Starter · #1 ·
Hello all, new to here and have questions maybe someone can answer. I buy and resell, repair and rebuild ATV's and I have one that is stumping me. I am working on a 2009 Kawasaki Bayou 250 and it runs rich. I have replaced all fluids, tires, new plug, tried a coil and CDI, new battery, non-ethanol fuel, ultrasonic cleaned the carb and all passages are clean. New bowl seal, new mix screw assembly, all o-rings are new, adjusted the valves, leak down check, float is set, but it still runs rich. Idles and cranks fine, runs a less throttle fine, very responsive throttle.

Can clean the plug, adjust to 1.5 turns out and runs like a champ for about a mile, then it will cut at full throttle (I mean WOT) and start hesitating when giving her the onions. Clean the plug, and its running like a champ again. Pops a wheelie in 1st and 2nd. Jetted main #120, pilot #22.5, both stock Mikuni. Do not know if the last owner used a knock off rebuild kit or not, but ordered Mikuni jets #110, 112.5, 115, 117.5, 120 new needle and new choke plunger.

My question is do these have a tendency to run rich from stock or later in life? I see some problems about carb issues with these machines, but this one is stumping me. I've even seen post on other boards from years ago when these machines were new about the dealers replacing the carbs because of carb issues, none seem to fit exactly what I am seeing.
 

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I have a 2008 I bought new that ran great for five months and suddenly one day started running rich and fouling the spark plug. I took it to the dealer the next day and they had to lower the needle in the slide. It has run fine since then. Try moving the E clip on the needle UP one notch. this will lower the needle in the carburetor and lean out the mixture.
 

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Discussion Starter · #4 ·
I have a 2008 I bought new that ran great for five months and suddenly one day started running rich and fouling the spark plug. I took it to the dealer the next day and they had to lower the needle in the slide. It has run fine since then. Try moving the E clip on the needle UP one notch. this will lower the needle in the carburetor and lean out the mixture.
Problem is no clips to move to. Single clip spot with washer, very very thin and didn't make a difference in rich when removed. Just got the OEM jets, gonna start testing and reading plugs this week. Carbs are time consuming, but very satisfying when you do figure them out. What you said about rich from the factory I am seeing more and more. They list another jet from OEM, but I bought OEM Mikuni jets from jetsrus.com. We will see.
 
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