Why is my bike Q running rough & guzzling fuel?
I have a problem with my 2007 Honda CBF500 which has got me stumped. It will start fine, hot or cold, and runs OK until you try to go over 5000rpm. Then it really struggles, and easing off the throttle a touch makes it more rideable. It has started to use a lot more fuel too, going from an average of 56mpg to below 40mpg. I have removed the carbs (not an easy job on this bike) to clean and check them, but there were no problems. Am I barking up the wrong tree, and could the ignition be at fault? Martin Lee, Ivybridge Answered by Scott Bullett, Doble Motorcycles Those are fuelling symptoms so I think you need to take a second look at the carbs. The float needles are wellknown for wear, with the brass seat where the rubber tip touches it starting to corrode. It might not even be visible to the human eye. Because it’s so tricky to spot, I mimic the probable scenario by getting the carbs off the bike and rigging up an auxiliary fuel supply. With the carbs on the bench at the same angle they would be on the bike I lift the throttle slides and squint down the venturis. If I am right you should start to see fuel well up around the needle and dribble down the venturi.
Sounds like your CBF problem is caused by worn carbs… see right