Throttle Body - Velocity Stacks
I know this is relevant for the A1 and A2 models
The standard throttle body rubber 'Velocity Stacks' have a lip near the junction with the throttle bodies,
Remove the passenger seat, rider seat, tank cover and raise the fuel tank on its rear hinge.
Prop the fuel tank up with the Kawasaki supplied 'Tank Rest Bar', clipped into the standard air filters,
if not a piece of wood or what ever will do.
Remove the air box/frame covers, look down through the 'Velocity Stacks', a torch may be handy,
and you will see the 'lip' near the bottom of the stacks. You will be able to feel it with your finger
Unbolt the velocity stacks and remove the lip with a 'Dremmel' type grinder and sand smooth. Job done.
When you replace the stacks, make sure that the stacks are clean, and line up well with the throttle bodies.
Boring the throttle bodies out to 47 or 48mm would improve air flow,
but from what I have been told, would only be beneficial if the engine were over bored and stroked.