This is a list taken from another site I frequent.
It is for Arctic Cats but some or all will work on the Kawasaki 650 or 750 V-twin

Rf Filter for the 04
Cats Belt reset jumper 04 cats
Set belt deflection-- This is cheapest way to keep from burning belts!
Keep choke cables lubed and protected they will get debris in them and stick.
Ignition control module
Install a Ignition Control module
VDI www.velocitydevices.com or a Moose www.moooseutilities.com
Larger or more aggressive tires
Clutch spring kits
Snorkeling is a greats way to improve water crossings.

This is a Basic overview of some tips and mods if anyone has anything to add please do.
If you want to do any of these mods and need help just ask