CB Caliper Rebuild

[MXSeatPro.com]

So I need some advice...I'm working on getting this bike road ready, that was last registered in 1984. I came with a dismantled front brake Master, but the caliper was still in tact. I put on a newer Nissin Master off a '05 GSXR, and had Stream Line make me a new line. I then filled and bled just to see what it would do and found the caliper wouldn't release. So I rebuilt the caliper and bled it again. Its been working perfectly for the past month or so until it decided to stay engaged again. What is causing this hang up and what tricks do you know to keep it from happening. It has a new seal and boot on it, and I thoroughly cleaned the caliper housing and piston. Is the new Master creating a vacuum? Is this common with late 70's Nissin calipers? Or is my best bet to just break it down and do it again? What are your thoughts on scoring the surface of the piston and creating a cross hatch to reduce stiction from the seal? Any thoughts?

 

[Powderfinger]

I'm not familiar with that particular caliper but there should be two pins that the two parts of the caliper slide back and forth on. Is it binding on these pins? Did you grease them when you put it back together?

 

[rockcitycafe]

could be the return hole in the master cylinder is blocked too.

 

[Hoosier Daddy]

The caliper can not create vacuum and if it could, it would not apply the brakes, pressure does that. As Roc City say's there is a tiny return hole at the base of the master resivour that relieves the applied pressure, if it is blocked the pads can't release. To check for captured pressure in the system, when the pads are stuck open the bleeder, if the pads release you have a problem not relieving pressure (master cyl).
If when you open the bleeder they stay applied chances are it's mecanical... Make sure the caliper is sliding freely on the slides #12 and the pads are free to move on the pins #15.

 

[MXSeatPro.com]

Great responses guys...I'll loosen the bleed to troubleshoot, but I think the return hole is blocked since the lever remains hard when it does this, as if the piston in the master isn't returning. I was unaware of this. I'll then polish #12's to allow it to float more freely. Thx Again.