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I'm working on a 400 big bear and I can't seem to get it to idle right. I've cleaned the carb several times. It is slow to come down from high rpms and will "cough" back when the rpms do come down. The choke isn't stuck, all passages have been thoroughly cleaned and the diaphragm is working correctly. Also, no cracks in the boot. What size main and mid jets go where? I may have swapped them on accident, the bigger jet is in the main jet spot right now. Could the calves cause this problem?
 

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This problem is very common with big bears. My 99 did it, and I found out the problem was a choked carb tube. My 2004 does it as well, and it may just be a matter of getting it warm before it starts to act normal. As far as I can tell you have done what you should to potentially solve the problem. It may just be the way it is. :/
 

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Big Bear400, What do you mean by a choked carb tube? Sorry I am highjacking this post but I got a Big Bear 400 from a farm, new piston, rings, cam, bored, valve job, OIL COOLER (that was broke and pumped the oil out so it fried the top end). I put it all together and it fires and runs and has good compression but it runs like crap and only with choke on. I have drained old gas, cleaned carb (quick clean and replace job not soaked). All works as designed, throttle and choke, but it does seem to be getting better the more I ride it. New ethanol free gas, one bottle of mechanic in a bottle, and a healthy splash of seafoam. I am hoping whatever is plugged up in some tiny port I didn't see will come out of there.
 

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Big Bear400, What do you mean by a choked carb tube? Sorry I am highjacking this post but I got a Big Bear 400 from a farm, new piston, rings, cam, bored, valve job, OIL COOLER (that was broke and pumped the oil out so it fried the top end). I put it all together and it fires and runs and has good compression but it runs like crap and only with choke on. I have drained old gas, cleaned carb (quick clean and replace job not soaked). All works as designed, throttle and choke, but it does seem to be getting better the more I ride it. New ethanol free gas, one bottle of mechanic in a bottle, and a healthy splash of seafoam. I am hoping whatever is plugged up in some tiny port I didn't see will come out of there.
I have the same problem. I have thoroughly cleaned the carb and installed a carb kit. I removed the fuel tank and drained it, cleaned it, added new fuel and added an in line filter. Checked all lines, air tubes, filter everything I can think of. It will run with the choke fully closed but at very high RPM. If I try and open it, it will backfire and sputter. If I open it completely it will idle so low it just dies out. If I try and give it any throttle with the choke in any position it will just die. It’s been very frustrating. I can't figure out what is wrong with it!
 

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We are having some 50 degree days this weekend so I am going to take my bowl off and check everything again as well as making an adapter to use my high volume brekekleen sprayer thru one of the tiny carb cleaner straws to give every orifice I can find a nice cleaning. I will update by Monday I hope.
 
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