Adjusting preload on a 04 Marzocchi Z150 fr!!!!HELP
 

Ok so I just got a like new 04 z150 fr (this is the coil sprong vision). Every thing seems to be fine and it rides great, but it is a little to "soft" for my style, and have bottomed it out many times:( ! I am just doing some research now on it and I guess the thing to do is adjust the preload. Now if only I knew what the preload was. I read some where that there is a air preload thing under the left eta knob, if there really is, how do I go about taking the knob of and is this really the right thing to do to fix my problem.

Plz help!!!!!!!!!!!!