Z1OwnersClub GB

Spent all day inspecting the brake calipers and renewing brake fluid in my Z900A4, only to find that when i put the caliper i had dislodged a seal and air was getting in. Anyway replaced the seal and bled brakes in under an hour, however, the brakes are now stuck on solid - the piston won't retract! Before I take a hammer to it tomorrow any ideas what the problem may be?

Just my 2 cents worth but I think your piston will be jammed by the seal, either the new seals are shite, they are not sitting right or there is some build up of possibly corrosion or some old deposit in the seal groove that is pushing the seal out of position and against the piston in such a way as to prevent it moving back.

Either the piston is stuck in the caliper (was it the original piston or a replacement ?) or the two bolts that the caliper mounting bracket slides along are stuck.
It's more likely the problem is with the caliper mounting bracket & bolts, which may just require stripping, cleaning & re-greasing.
Another possibility is that one or both of the bolts could be bent slightly & not allowing the caliper mounting bracket to move back once pressure on the psiton is released.

can u push piston back if u slacken bleed nipple ???

Did you use any other type of cleaning fluid whilst fitting the pistons/ seals?
e.g WD40 release spray, this does swell the seals, maybe stuck or nipped the seal.

stu

Cheers for the help guys, not too sure what i'd done but I need a new piston one side and a seal on the other. Best change both on each side me thinks.

Just make sure the groove for the seal is good and clean, also, I always use a little rub brake fluid on the pistons and seals when assembling calipers as a lubricant.

Was there not a post or two from other members a good while back about trouble with certain replacement pattern seals