front master cyl bleed ?

[6m459]

Hi,

 

I have had the front brake lever / master cyl assembly off my red bike to fit a new sight glass.

 

The brake worked fine before this, so I know all is well except that I have let a bit of air in up top.

 

After re assembly, I have air in the system and soft lever action but I know its all up top at the reservoir end.

 

Whats the simplest way to re prime the master cylinder in this case?

 

(Sorry for what might be a well addressed question, but I am under the gun a bit as my temporary permit for this bike expires after tomorrow and I have to get it to the inspection station before then or legally it becomes a paper weight. They seem to think front brakes are important.)

 

Thanks,

 

Brian H.

[met128]

Break loose the banjo bolt on the master. Bleed it like you would a bleeder (pump it, pump it, hold it -open the banjo - Repeat a few times). Then bleed the caliper

[dingy]

I am having the same exact problem.

 

Rebuilt master, calipers & new S.S. lines.

 

De-linked brakes with an RSV splitter.

 

Have pulled master apart and it is rebuilt correctly, no nicks in seals & bore is fine.

 

Large and small hole in master are open.

 

I have speed bleeders on it.

 

Have tried a mighty vac and am able to pull fluid through calipers.

 

Also made a plate for top of master cylinder with a fitting in it and tried to pressurize master to push fluid through with mighty vac.

 

But no real pressure being developed at master cylinder.

 

I will try loosening upper banjo bolt and see if this works.

 

If this doesn't work I am going to put standard bleeders back in and see if I can get higher flow rate than with speed bleeders in an effort to pull air that must be in there through.

 

Did rear brake & clutch master & slaves and they are fine.

 

I almost wish I were bald, I wouldn't be pulling my hair out over this one.

 

 

Gary

[dthomso1]

I had the same problem - don't give up as it will eventually sort itself out!

 

What you might want to try, if you have one of your old brake lines left over is to remove the banjo bolt at the master, push the brake line to one side and re-attach the old brake line (make sure it is crud-free inside). Pump the brake, returning the fluid into the master through the old line. This will eliminate any air bubble at the top end of the master. Put your new line back on and continue to bleed the caliper and damper.

 

The other thing I discovered was that the dive dampers are a bugger for hiding air bubbles. With the help of a Mity Vac and a lot of patient pumping, you will eventually eliminate them. It took me at least a dozen episodes of bleeding the system before I was confident that I removed all the air.

 

Good luck!

[6m459]

As is often the way, I soon had it resolved after some lunch and a sit down.

 

When I got back, I loosened the banjo bolt at the reservoir and squeezed the brake lever.

 

Then I held the lever down as I re tightened the banjo bolt.

 

Once the banjo bolt was tight, I released the brake lever again.

 

I repeated the above about 3 times and all was good.

 

Thanks for the ideas.

 

Brian H.

[dingy]

Loosening the upper banjo bolt did allow partial pressure to be developed.

 

Still not enough though.

 

I a going to let it set a while to let mall bubbles gather together

 

I don't have the hydraulic anti dives any more, went to electric. So t least don't have o mess with them.

 

 

Gay