Topic: hydraulic brake pressure

[wilson11]

Does anyone know the PSI the brake system operates at? Is it the same for the pushing of the piston and the retraction of it? I have been having problems with my brake piston (cb400f) not fully retracting into the bore after use. I have cleaned the caliper groove to the point it takes 7-8 PSI to slide the piston into the caliper with the seal in. Is this okay or too much or to little? I sure would like to solve this problem before summers over.
On another subject are there any websites on the early cb450(66-69) that are out there. I am looking at a 68 model and would like to get some more info on them. I know they are DOHC and this is SOHC but I thought I would ask anyway. Anybody has any feedback on them I would love to hear it.
                                   Thanks

[Bob Wessner]

Does anyone know the PSI the brake system operates at?

Not sure it operates at any particular pressure, just the multiplier affect of hydraulics. I seem to recall it's something like 7 times the manual (lever) pressure.

[Paul]

OK I'll try again, hopefully I won't get it bassackwards again.
The piston being pushed out under hydraulic pressure is mostly to put pressure on the disc (as opposed to getting the piston to move out)
There is no actual pressure to retract it but the action of the release of the pressure and dare I say... a flip action of the seal (heard that somewhere)
certainly the movement of the disc, the pivot spring etc will just cause the grip to release.

Your problem may be the return system in the master cylinder by the lever, not allowing ....what.."back flow" which will prevent the piston from "relaxing"
Can you push it back by hand whilst all piped up?

[Bob Wessner]

Your problem may be the return system

If this is the case, and it seems possible, there is a very small hole in the master cylinder that may be blocked. It is toward the hose outlet end of the master and at the bottom of a depression. Quite hard to see actually.

[wilson11]

I can push the caliper back in by hand when the system is pressurized and I can even hear fluid going back into the master cylinder. I  rebuilt the cylinder and put on new hoses as well but perhaps a error in the assembly of the cylinder occured(hope not).

[Bob Wessner]

perhaps a error in the assembly of the cylinder occured

I screwed up mine the first time  , might be worth a look.