After the K8 restoration, although the front caliper piston had a wee bit of corrosion, I couldn't resist trying it on for a test ride.
Good news - no leaks. Bad news - lever pulls back all the way to the grip with 20% stopping power. Pinched the brake hose near the caliper steel line - lever now hard as a rock. So we are down to something amiss in the caliper, and it wasn't air or pad running clearance.
Noticed that on brake application the rotor was being forced sideways maybe 5 thou. Loosened the 3 caliper to fork bolts, rotor movement is gone but lever still soft.
Read the forums, scratched the noggin, and made black brain clouds. Finally it came - the fender bracket was between the caliper hinge bracket and fork - it looks perfectly OK assembled, but an inconspicuous picture in a manual says not.
Put the hinge to the fork direct, problem solved. Not that any of you would make this mistake, but one of your DPO's might have.
Still looking for a piston.
