QuestionI have a '90 Honda NX 250. Lately the front brakes are staying stuck after i pull the caliper. I tried to disassemble it but he brake 'pistons ' are so stuck they won't let go of the disc. Can you give me any tips on retracting the brakes so to remove the front wheel and brake assembly to service it?
Thanks
AnswerEd, open the bleed valve on the caliper, which will release a little of the pressure. Sometimes you can use a real large screwdriver or lever to get in between the pads and disc to push it back a smidge.
Once you get the caliper off (you don't have to pull the whole front wheel), you can use the master cylinder to push the pistons out of the bores. On a double piston caliper, you have to use a block or c-clamp on each one to allow them both to come out a little at a time, so they will pull out with your fingers, once the ends of the pistons pass the seal rings.
Once it is apart, remove the square section seal rings and disconnect the caliper from the line. Clean the caliper body thoroughly, with special attention to the grooves where the seal rings seat. The corrosion build up there is what causes the seal rings to seize the pistons in place.
Reassemble with fresh seals, usually you can reuse the pistons unless they are deeply pitted. If they are you can often clean the pistons with alcohol or chemicals to clean off the brake fluid residues, then apply a little JB weld epoxy to the pits. Get it as smooth as possible then let it dry overnight. Carefully sand down the excess until you get a smooth surface, then reinstall the pistons and the rest of the parts. Be sure that the master cylinder is clean, especially in the floor of the reservoir where the tiny bleed hole is located. Bleed carefully and go riding again.
http://www.xs11.com/tips/maintenance/maint6.shtml
http://www.bluepoof.com/motorcycles/howto/svs_bleeding_brakes/
Bill Silver
