Two pot brake caliper - one seized piston now removed
Feb 11, 2020 17:38:13 GMT
ian and bodie like this
Post by Dennismenace on Feb 11, 2020 17:38:13 GMT
One of the front brake calipers on my CB400NC is leaking despite new pistons and seals. I was lucky enough to buy a box of odds and sods last week that contained a caliper and I decided to refurbish it. However, one of the two pistons was missing and the other was seized solid.
I tried penetrating oil for several days, heat and brute force without success. There was not enough of the piston proud of the bore to get grips on it. I cut some small channels in the top of the piston and used an old chisel as a bar to twist the piston and I got some movement so I knew the piston was at least rotating in the bore.
I have an old piston from refurbishing the (now leaking) caliper so I fitted that using the old seal that was still in place. I tried to blow out the stuck piston with an air line using a wood block to keep the the other piston in place but even 100 psi would not shift it. I sealed the banjo bolt with a collar and washers so that I could fill the removable pot with brake fluid. Then, I compressed the moveable pot in a vice using a socket. After some grunting by me the seized pot began to move and eventually came out. It is amazing how efficient the old seals were in both the seized and moveable pot. This shows the power of hydraulics.
Before using the vice I tried attaching the caliper to the bike and using the master cylinder to push the piston out but without success. I doubt that the master cylinder would have produce enough pressure to pop out the caliper piston.
Dennis
I tried penetrating oil for several days, heat and brute force without success. There was not enough of the piston proud of the bore to get grips on it. I cut some small channels in the top of the piston and used an old chisel as a bar to twist the piston and I got some movement so I knew the piston was at least rotating in the bore.
I have an old piston from refurbishing the (now leaking) caliper so I fitted that using the old seal that was still in place. I tried to blow out the stuck piston with an air line using a wood block to keep the the other piston in place but even 100 psi would not shift it. I sealed the banjo bolt with a collar and washers so that I could fill the removable pot with brake fluid. Then, I compressed the moveable pot in a vice using a socket. After some grunting by me the seized pot began to move and eventually came out. It is amazing how efficient the old seals were in both the seized and moveable pot. This shows the power of hydraulics.
Before using the vice I tried attaching the caliper to the bike and using the master cylinder to push the piston out but without success. I doubt that the master cylinder would have produce enough pressure to pop out the caliper piston.
Dennis
