I just bout a 93 cbr f2 but the healdlight doest turn on at all. i checked the fuse and i went as far as changing the wiring harness.

 

Assuming you changed the bulb, too, I would check the contacts of the light itself, where the plug from the harness attaches, and see if it's corroded or loose. Maybe check ebay for a new light altogether: click me.

 

I had the same problem a couple months ago. It ended up being the electronics in the run/stop switch on the handle. The power runs from the battery to the left clip-on (hi/lo beams) then to the right clip-on (run/stop) then to the head light. Check all the wiring going from the left to right clip-ons and then from the right clip-on to the head light. Hope that might help.