www.zxrworld.co.uk

My bike has suddenly started running a bit lumpy lately.

Its actually a zx6r, not a 400 but anyway, the powers a bit on off low down, sort of below 5k. Can clear it through using plenty of throttle but its a bit of a pain when cornering. Its also got a huge flat sport at around 9500rpm, but only noticable in the higher gears i.e 4,5,6. Sounds ok when idling.

Any ideas what this could be? Have got some new plugs im gonna put in today see if it makes it any better.

could well be the plugs coking up mate if they are old, i would check the air filter & fuel filters too, when was it last serviced?

That also sounds like what my 400 was doing through the winter, when the
carbs were icing up. The icing was blocking the smaller jets, but when
you opened up the throttle, onto the main jets, it was fine, but same as
you, slowing the revs for cornering etc was a pain.
If the plugs are not at fault, check for crap in the carbs, and the fuel
supply/filter.