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Old 06-17-2017, 11:38 AM
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Default sputtering

Hello, I have a 1996 Yamaha Big Bear 350 and it was running fine just a little while ago. All of a sudden, after about ten or fifteen minutes of driving it will want to lose power or sputter. Right now, It'll turn over by new battery for 1 minute if I have to, but it won't kick in. It used to start after a few seconds. The only way now I have to get it started is to press start button and hold throttle wide open for it to attempt to start, and then after a few attempts it will finally go on its own, while slowly letting the throttle out or back. When and if I do get it started and going, it will be fine for about ten minutes, then start to lose power. Any answers.
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Old 06-18-2017, 03:02 AM
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Could be anything, but symptoms seem like those of a way too rich fuel/air mix. Remove the plug, if the nose is black and sooty, you probably have a rich mixture. Fit a new plug and check the air filter is clean and that the choke isn't stuck. If the plug isn't sooty, it could be low compression, probably caused by the valve clearances being wrong. Re-gap them anyway, then, if it is still bad to start, do a compression test, over 90psi is OK.
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  #3  
Old 06-19-2017, 11:37 AM
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Default sputtering

It seems to run fine again. I don't know how I got in there but I turned that one gold screw in a bit, the one thats underneath the carburetor. Big black hose was in the way too. It ran ok, but the one thing I am concerned about is Why does the bike seem to want to sputter or lose some kind of power whenever I make a turn. To me, it seems like theres something wrong with float level maybe. Everything else sparkplug etc are ok.
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Old 07-24-2017, 01:10 PM
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I checked the valve clearances and just had to adjust intake, exhaust was good. I guess you could say I have rich mixture because sparkplug is sooty. But I think I already tried working on that ( the screw underneath carb). No difference, still chokes or sputters.
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  #5  
Old 07-25-2017, 03:44 AM
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Never alter that screw under the carb, it is the idle mixture screw, set at the factory and does not need adjusting. A rich mixture is caused by a clogged air filter, choke sticking on, worn main jet, or float level wrong. On most modern carbs the float level is fixed, check out the other possibilities before assuming it is wear in the main jet or needle. On some, the needle can be lowered further into the jet by changing which groove the circlip holding it is in.
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  #6  
Old 07-26-2017, 02:42 PM
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OK, If I just buy a whole new carb and install it myself, because I could weed out the first two problems, would that solve it?
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  #7  
Old 07-27-2017, 03:05 AM
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If you bought a genuine carb from Yamaha, yes. If you got a Chinese copy, no. They have to be set up to suit your engine. With copy carbs, that adjuster I told you not to alter will not have been set "at the factory," and judging by many posts on here, the copy carb may not even have the right jets for your engine in it.
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Old 07-31-2017, 03:57 PM
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Your right, Because I just went on Amazon and Ebay etc, and the carbs, for my bike anyways, were only like $69.00.
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Old 08-01-2017, 06:54 PM
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I didn't read anything about cleaning the carb.
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  #10  
Old 08-03-2017, 03:16 PM
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I had it cleaned and blown professionally 6 yrs ago. I think I read somewhere that when reinstalling carb, are you supposed to fill the bowl with gas?
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