Divvy bogging down at high revs

[knocker]

Recently i've noticed my 600 divvy has started to bog down at high revs and it's put me in a bit of a messy situation twice when i've gone for an overtake only to get to about 7k revs and then hit some huge flat spot and looked a right lemon as I ever so slowly creep past some fully loaded bus.

It runs fine at lower revs and only bogs down if I suddenly open the throttle, sometimes it's just a flat spot and other times the bike judders as if it's being starved of fuel until I wind of the gas.

I have next week off work so plan on giving the bike a complete going over ready for winter and it's always handy to have a few pointers before I start.

So, anyone any bright ideas?

[serlant]

first guess would be air filter.

[P.addy]

what colour is your spark plug, sounds like mine...which is running richer than bill gates at the moment..