Yep,could be the fuel filter,as Skids said.The filters are around 6 or 7 quid to replace.If your Duke dealer has'nt got one,go to a BMW dealer.(Take the old one as a pattern.)
Forgot to mention,the filter is inside the fuel tank.Get to it by removing the filler cap and boss,then unclipping it from the tank along with the pump and pipework.(Its better if the tank is drained first!
)Its an aluminium cylindrical thingy!
[Edited on 13-8-2004 by KeefyB]