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Discussion Starter #1
Has anyone had any problems with a vstar 650 only running on one cylinder? My wifes 04 only has 2400miles on it and under any kind of load it only runs on the front cylinder. It starts and idles fine on both but the minute you try to go with it you only get power from the front cylinder. It started as a bucking when rolling on the throttle and got worse and worse till it's almost unridable. We took it to the local "garage" bike mechanic and he pulled both carbs for cleaning and also checked the fuel pump and replaced the plugs. He said the carbs looked brand new(which with only 2.4k on it they should), he felt so bad that he didnt' even charge us for the work he did. He suggested filling it with good clean gas and trying to ride it for a bit and see if it clears up. It has straight pipes and was jetted when they were put on. My wife is the 3rd owner and she had no problems with the bike prior to this.
If I start the bike and while idleing I can feel that both pipes are pushing about the same amount of air. But once you start to bring the rpms up the rear cyl. starts to stumble and you can feel the stumbling in the exhaust flow. The Mechanic says it appears to be starving for fuel, but now I'm beginning to wonder if there is a spark problem with it. If you rev it when you shut down the throttle there is a lot of backfiring in the pipes, which tells me there is a lot of unburned fuel running through the pipe. This seems odd if it is staving for fuel.
Is there anything that can happen to the spark when increasing the rpms that doesn't happen at idle? Has anyone else had problems like this?

thanks
 

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Discussion Starter #2
Do these bikes have any kind of spark advance that could be messing up and causing a loss of spark when the rpms are increased?
 
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