QuestionQUESTION: This is a new bike with 2700 miles on it. At 1700 miles I had Vance And Hines install their straight shot pipes and jet kit on the bike and tune it. For the next 1000 miles the bike ran great. Then it began backfiring excessively, failed to hold idle and misfires at high revs. Air intake and filter checked out. I'm baffled. While this could be a lot of things, obviously, the newness of the bike has me perturbed. Where should I look first?
ANSWER: Alex, you didn't indicate the year of the bike but the backfiring is an indication of a lean mixture and it consistent with the poor idle and high speed miss. I'm not sure if the new exhaust is the cause or just coincidence in timing. Did it start to act up all of a sudden or in the spring after sitting all winter? If the bike has not been ridden in a while, I'd suspect it might need a carb cleaning. If it started happening all at once, you need to find out what's preventing the fuel from getting to the carbs. Some fuel is getting through or it wouldn't run at all. Does the bike run a lot better for a few minutes when the choke is applied? If so, it confirms the problem is in fuel delivery. I guess the first place to start is the fuel filter. Make sure it's not plugged. Secondly, is the fuel pump delivering the right amount of fuel? You can pull the fuel line off the carb and catch the fuel in a suitable container while cranking the engine for a few seconds. There should be plenty of fuel coming out of the hose. (I don't have to tell you that you should not smoke when doing this and not to do it in a closed garage with a NG water heater going!) Gas can be pretty exciting if mishandled. Lastly, open up the drain screws on the bottom of the carbs and crank the engine. There should be a steady stream of fuel coming out during cranking. It's possible the floats are stuck in one position and not letting the fuel into the car bowls. If that's the case, it's a carb clean again.
Good luck...let me know what you find.
Rich
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QUESTION: Thanks Rich. Great information. BTW, the bike is a 2007. Yes, to both questions. YEs, it runs better when the choke is applied. Yes, it started running poorly all of a sudden.
I drained the gas and replaced it. Still no improvement.
I'll try the fuel filter next as that is the least costly fix.
If I have to do a carb clean, what can I expect to pay from a dealer? Is this a timely process with disassemble? Or ??
AnswerWell,I can't say what it will cost because shop rates vary quite a bit. A knowledgeable mechanic can do the job easily in 3-4 hours including rebalancing the carbs. It will partly depend on how much extra stuff has to be removed to get the tank and carbs off such as fairings, sound systems, etc.
Regards,
Rich
