we recently changed the standard front fork springs of our 2006 KLE 500
for Wilbers Racing ones, progressive. Boy that made a difference. The bike doesn't dive as much under braking, but more importantly has better road contact through corners, where surface is more on the rough side. The feedback is so much better.
Unfortunately, for me as a dad, our son is now curving on the foot pegs through corners, as he feels the bike has become more direct, more predicatable. He never did that with the old springs, as he felt not 100% in control.
About two weeks after we have changed the springs we have also changed the front brake hose for a steel flex one, and it really has transformed the bike into a very nice unit. If you pull the lever, you can now hear the tyre scream, if you want so. Now you can talk of stopping power even with two up, which was a vague expirience before.
For a relativly small amount of money this bike is now a pleasure to ride.
Next project might be the seat....
Cheers from downunder, Michael
P.S.: Adding air pressure in the front fork will make them stiffer, but even less sensitive. By their design those valves are only there to release built up pressure in the fork after hard riding. That is to my understanding.