so this f4 i recently bought has a problem with the braking. when i apply the front brake i get a shimmy in the front end. kind of feels like a pulsation from a warped rotor. any suggestions on what to check? i dont want to go buy new rotors and have that not solve the problem. can anyone suggest anything? thanks

You can put a dial indicator onto the bike and spin the wheel while the pin sits on the disc. You don't want to have a high amount of run out. If you do there are not many people that will even attempt to machine the disc so the only option will be to change the disc. You can try running some sand paper on both pad and disc. To see if there is a small difference when reassembled and braking :)but if the discs is warped this will be fruitless.

Ditto what Marinko said. If a rotor is warped it'll send a helluva pulse through the brake lever when stopping from high speeds. You can check to make sure the caliper bolts are tight and that the pads still have life but I'd say from your description that the rotors are warped.

thanks guys, how many thousanths of an inch maximum runout do you think i should have before it will be felt?

Brake disc max runout on the 1000RR is 12 thousandths. Don't know how much it'd take before you felt it through the lever.

thanks for the help guys:D i'll measure my runout and see what happens