Topic: Brake master - can't bleed??

[Justind97]

Hey guys,

Not an SOHC4, but a racebike nonetheless.

INFO:

I have an RZ350 front end.   Stock calipers, stainless lines and a Brembo REC 13mm Master ( https://store.bevelheaven.com/brake-related-parts/13mm-rec-brembo-master-cylinder-front-brake/ )

Calipers (2) are Single piston each.  38mm diameter.

PROBLEM:

I can't seem to build pressure in the bloody thing.  I have a Mityvac style bleeder.  The brake handle is the highest point in the system. The lines go straight to the top.  The caliper pistons were pushed in.

This is the second master that I have gotten, so I know it's something to do with my setup.  I mounted the original master back on and it bled in no time. 

Is it possible that I'm pushing too much volume through the lines and there's no pressure building up?

My caliper bolts weren't super tight, so I could see the calipers flexing when I pulled on the lever.  I decided to pull the bike off the stand and see if it grabs.  I would say there's about 5% brake power going to the rotor. If I applied weight and pushed, it would give way.

Any suggestions?? 

[Stev-o]

I had a difficult time with my RD350, bought a power bleeder and got the job done.

[Justind97]

I'm using a power bleeder (mentioned above).

[bwaller]

If the air can work straight up to the master, leave it for a bit then try to bleed it at the master itself. Just gently tug the lever a smidge over & over to see if you get some air through the cylinder.

Are you using one line per caliper and a double banjo bolt at the top?

[Justind97]

One line per caliper and a double banjo on top.   3 washers on the banjo.

[bwaller]

I'm likely not telling you anything new but those damn banjo's hold air like a bandit. Change the angle of the master as much as you can to rid the trapped air and bleed as much as possible through the master. The other (dirty) option is bleed through the banjo bolt, loosen & tighten while working the lever to see if you get any.

Short story I've only had one master cylinder that wouldn't bleed, damned early GSXR model and I worked for hours. Threw on a different one and it bled in minutes.

Sorry not much help. 

[turboguzzi]

first of all, 13mm on double calipers sounds very small, more like single caliper stuff. i run brembos f08 that are also 38mm and use a 5/8" circa 16mm MC.  vintagebrake.com has a table fpr calculation BTW.

had a bad experience with a rear brembo caliper that wouldnt bleed, turned ouot to be a design or mfg error and had to modfiy the front spacer to make it work. i live in italy but sometimes not really amzed with the quality control of some of the stuff made here....

a usefull tip is to put some teflon tape on the bleeder's threads and do a backward purge pushing liquid form the nipples with a syringe. if liquid doesnt easily flow into the reservoir, then you have a problem like in my rear M/C

[POPS 911]

BACKWARD PUSH with a 20 gauge needle, flex hose on end secured with a screw clamp and full of dot#3 and cap off of master cylinder. Push slow and steady.
Pull out the bleed valve and clean out = I use a hand drill to clean out passages, crud from old fuel can block the flow.  Did you say RD350 KENNY ROBERTS Black and Yellow = my California son has 6 of these with all the racing farings and built motors  with one stock bike he bought new.

[joesmotos]

I had a bike once that refused to be bled...(that sounds weird)

Anyway..in a nutshell...i unbolted the calipers from the fork..stuck a piece of thin wood in between the brake pads...and got a rubber mallett and started tapping on the calipers while lifting them up and sort of just rolling them around to different positions..while my buddy gently squeezed the lever...tiny air bubbles started rising into the master cylinder and slowly but surely it bled out,took a little while,air gets trapped in weird places for whatever reasons..and yes,i tried the Mity-Vac thing,power bleeding,etc etc..

basically by rotating/twisting the calipers into different positions,and tapping on them,the air bubbles found their way out..looked silly as hell at the time but it damn sure worked.