had this problem on my mates pulsar. we thought that we'd be clever, and use heat to free them up. so we removed thecaliper from the car and took it upstairs to his flat to use the gas ring to heat it up. so there we were, 3 of us standing around the cooker. two holding on to the caliper with mole grips, and the other one trying to twist the pin to free it up. it started to turn slightly, so we thought we were making good progress - then all of sudden it flew out like a bullet and somehow missed us all and embedded itself into the skirting board. we hadn't thought about the expansion effect from heating the grease behind it