i was noticing some brake drag noise and decided it was time to clean my brakes, since i hadnt done it sine i got the bike 2000km ago and have now clue when the previous owner did. i took the pads out and started cleaning with a tooth brush and soapy water, but no matter how much i clean i cant seem to get all four pistons to come out equally at the same time. and they dont seem to retract back into their slots either once theres no brake pressure. any ideas? the bike is a 03 cbr600rr if it makes any difference

 

There is probably some junk/debris inside the caliper behind the pistons and/or in the bore that's keeping the pistons from moving smoothly. Most likely you will need to disassemble the calipers by removing the pistons and clean out the calipers & pistons to get everything working right again. It's a pretty easy job to do with the calipers removed & sitting on the bench.

 

I clean my calipers completely every 6 mo.I take the caliper apart and clean the pistons very well and also clean the pins that hold the pads in place.You'll be surprised how much build up is in there.

 

The pistons don't actually retract during use. The slight run-out tolerated in the design
will push the pads away (by a few thousandths of an inch) from the rotors,
when pressure is released from the lever. As mentioned by the previous comments,
most brake drag is from the calipers not riding smoothly on the hanger-pins that the
calipers 'float on/mount from' the forks. The rubber accordian boots should be cleaned
and repacked with grease to facilitate their ability to 'float' on the pins inside.

There are several good picture "how-to's" on these forums + some great video on you-tube.

Hope this helps, good luck, Ern