Why is my bike Q run­ning rough & guz­zling fuel?

Motorcycle News (UK) - - Garage -

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

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