back brake bleeding

  • Thread starter Thread starter lemonjelly
  • Start date Start date
Hello,

After bleeding I always leave the brake overnight with the lever actuated (tie it to the
handlebars). Then, in the morning, the brake has always got some extra pressure (although
my buddy states it couldn't be......).
Why shouldn't that work on the back brake, too, if you HAVE pressure at all.
Find a way to tie the pedal down.

Ernesto
 
Good tip Ernesto, I didn't try that.
I am not sure why this would work either, but if it does then we shouldn't knock it.
The feeling of relief is still strong, I pop into the garage every now and then just to check it wasn't all a dream and that the brake works. At this rate I will wear it out!

SimonR
 
Dellortoman said:
Just be thankful you don't have a Benelli Sei or a Moto Guzzi with linked front and rear brakes. They're a real bastard to bleed.

Cheers,
Cam
Click to expand...

You should try bleeding my K1100RS with ABS! I had to buy 5 speed bleeders to get it right!
 
I recently met my match with the rear brake too. I fitted a braided line on the rear brake on the RGA, rebuilt the caliper and the master cylinder (brake pump) only to discover I couldn't get the pedal to register any resistence at all.  I removed the caliper from the wheel for bleeding, twisted it this way and that, raised it and lowered it.  I used the vacuum pump, I bleed it in the conventional manner. No joy. In the end  I bought a new Moto Guzzi master cylinder that gave a slight suggestion of braking power on the system.
I have since abandoned any further efforts as well as hope of getting stopping assistance from the rear.
 
Glad i m not alone I have to say mine is working slightly not as good as my previous postsuggests now i ve ridden it a bit but i still have to do it again using Keihs method of removing the circlip and using the screwdriver ,

Shaun
 
Well, if I knew what I had done?
However, if I started all over again I would put the caliper high, use the Mityvac on the caliper and try Ernesto's method of depressing the lever and leave it alone for a while. Finally the series of short pumps seemed to really get things done after bleeding the caliper, perhaps some air around the master cylinder piston was ejected into the reservoir?

SimonR
 
When I bought my '78 Jota, on the first ride out of the crate around the block the back brake began to bind until it was almost locked solid. Stopping and pumping the pedal a few time freed it, but the rear rotor had got so hot the paint had peeled and the rotor actually cracked. Might have been like that before I got it, I didn't notice, who knows.
Anyway, I rebuilt the caliper and the master cylinder. The old fluid was obviously very old, it was crawling and it stank, but of all the drinks I've drank, I'm most grateful to that one from Gun ... whoa, off topic there! :D When I tried to bleed the system I couldn't get any fluid to move out of the master cylinder at all. I pulled the piston out and (I don't remember why now) scratched the inside wall of the master cylinder with my fingernail. To my amazement it had taken on the texture of cheese, scraped away easily just with a fingernail.
So I got a replacement master cylinder, vaccuum bled it, and have no trouble since. Really odd, I've never heard of that happening before, but how many people scratch the inside wall of their master cylinders when they rebuild them?

Ken
 
Lawrence,

Have you made sure you've put the thin spacer washer in the right place. It goes on the inside not the outside. It's purpose is to locate the piston in the right spot so one hole is open and the other is closed. Mine came like this and when I rebuilt the master cyclinder mine didn't work either. I didn't have a clue until a mate who's an ex Superbike race mechanic up here pointed it out to me.

Cheers
Chris
 
Hi Chris,
With my wrenching skills, I suppose that I could have easily placed a washer in the wrong place :-( But with the cost of a completely new Brembo rear brake pump being so economical, I'm not about to return to mucking about with the original pump that I 'rebuilt.'  I just threw it in the parts box and went riding.  ;)
 
Had this problem on my old Jota,it was useless from the day i bought it so instead of all this bleeding, stripping and messing about i came up with a much easier solution. Don't use the back brake. Not much help but worked for me!
 
Dellortoman said:
Just be thankful you don't have a Benelli Sei or a Moto Guzzi with linked front and rear brakes. They're a real bastard to bleed.
Cheers,
Cam
Click to expand...

I don't have a problem with the Guzzis at all.

There are a couple of tricks to all of this. I'm not saying that all of these apply all the time.

Dot 3 fluid is slipperier than Dot 4. Sometimes the seals bind and the spring isn't strong enough to fully return the M/C piston. Dot 3 will often remedy this but you will need to replace fluid more often as it is more hydroscopic and has less of a heat range.

Make sure the lever adjustment allows full return of the piston.

I pressure bleed. I use a reservoir cap with an air inlet in it. I use just a few psi of air to slowly push the fluid through. Do it fast and you will get lots of bubbles. Do it slow and it allows a very easy one man operation.

Be prepared to crack a few joins in higher parts of the system. Reseal as soon as the bubbles disappear. Naturally clean off any fluid.

If the rear caliper is below the M/C then you can gravity fed fluid back from the bleed nipple. Have clean fluid in the tube attached to the nipple, open the nipple just a bit then crack joins that aren't as high as the tube fluid level.

Just a few things I do. Guzzis are easy-peasy. I would expect Lav's to be similar.

Cheers

Rod, new to Laverdas

 
I should have paid more attention to Jugs_s.
I was working on another rear brake master cylinder the other day and found that the tiny hole he was talking about was blocked!!!!!!!!!
With that hole blocked then the air cannot escape from between the piston seals and thus prime the 'pump' or master cylinder.
It is an important thing to look out for and may be the cause of some peoples inability to prime.

I used some Oxy-Acetylene nozzle cleaners to eject the crap - boy was it solid! It took some shifting.

Regards
SimonR
 
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