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Hi, I have a 2007 big bear 250 that has a Carb issue that I'm stumped on. I bought it not running and found that the previous owner had replaced the intake boot with an after market one which was wrong and not making a seal on the Carb. I replaced it with one I got from the Yamaha dealership in town and while I had the Carb off I gave it a really good cleaning. When I got it all back together it fired right up, revved up good with the choke on and idled perfectly, but when you give it any amount of throttle it bogs down and dies. It will do this with the mixture screw all the way in or out. I took the Carb off and inspected everything but can't find a problem in it. I found an article about people mixing up the main and secondary jets and having similar issues but I triple checked that the larger jet was in the main jet emulsion tube and tightened down fine. If I remove the air filter and block half of the intake off it will rev up much better so I thought it was running very lean, but the spark plug is jet black. I'm at a loss, anyone have any ideas on what to try? I thought of adjusting the vacuum slide needle to a more rich mixture but with the bike being factory stock I wouldn't think it would need this amount of adjusting.
 

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I attempted to adjust the needle last night and sent the top screw piece rocketing off into unknown territory. Spent an hour searching for it but it is gone... I was looking on EBay for a new one to use and came across a complete brand new carburetor for only $70. To me that sounds too cheap to be considered reliable, but I am thinking of giving it a shot. Does anyone have any experience with these cheap carburetors?
 

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Carb

Hey man I have bought several carbs off of ebay, 60-80 is usually the price i pay. I gave em a good cleaning and they always worked fine. Or if you want to work on you problem I would suggest getting a cutting torch cleaner and running the smallest rods through the jets, sounds to me like a jet or the atmospheric vent for the bowl is partially blocked.
 

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By some stroke of luck I found the missing part. Spend an hour looking for it, shake the hell out of the ATV to see if it falls out, get angry then give up finding it. Gently push the ATV out of the garage and it reappears. I decided to give the original Carb one more try and sprayed out all the jets and reassembled the slide and slapped it together and for some reason it runs better than ever. The only issue it has now is a bogging out problem when going past 1/2 throttle but I'm hoping I can adjust this out with the mixture screw or needle setting.

Thanks Yamahogz for the review, this is my first ATV but have been a motorcycle guy for years so a carb under $100 is an extreme shock for me (I paid $600 for a Carb set on an old gl1100 and felt like it was a good deal lol).
 

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sounds like the float is set wrong and you are running out of gas from the bowl
 
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