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Blood Sweat Tears and Grease => Wheels Tires and Brakes => Topic started by: imwastefull on May 10, 2019, 20:50:36

Title: Please, help me bleed my custom brakes.
Post by: imwastefull on May 10, 2019, 20:50:36
I built this bike a couple years ago but the brakes we always sub-par. This winter I redesigned the system and now absolutely can not get them to work. Here's the set up -

Brand new 3/4" master
Brand new -3 an braided lines
Two (not rebuilt) but perfectly working Brembos
Brand new aluminum crush washers everywhere.
Dot 3 synthetic fluid.

For whatever reason, I CAN NOT get pressure to build. But, as near as I can tell, I have no air in the lines. I have a mity vac and I've pumped 3 full resevoirs full of fluid and it's all clean, no bubbles. But, I step on the pedal - nothing.

When I break the bleeders, clear fluid, no bubbles.
I've bled the system at all of the banjos.
I've used my my mity vac until the cup is completely full and there's just no pressure.
No leaks anywhere. No bubbles coming out.

Anyone have a clever suggestion?
Title: Re: Please, help me bleed my custom brakes.
Post by: imwastefull on May 10, 2019, 20:51:40
Pics
Title: Re: Please, help me bleed my custom brakes.
Post by: imwastefull on May 10, 2019, 20:53:08
Pics
Title: Re: Please, help me bleed my custom brakes.
Post by: Streetfighterkz on May 10, 2019, 21:26:48
Cool looking ride. 

Im thinking your M/C has too small of a bore. Im running a two piston Brembo (designed for rear use) on one of my bikes. From what Ive researched the stock M/C that Ducati used with that same caliper is 11mm (.433 or 7/16). Front brake setups with the calipers you are using typically have 5/8 bores.  Basically what Im trying to say is the M/C may not be able to push enough fluid to activate the brakes before the plunger/pedal runs out of travel.

Later, Doug
Title: Re: Please, help me bleed my custom brakes.
Post by: imwastefull on May 10, 2019, 21:36:14
I'm sorry, it's a 3/4" master. I just noticed the typo.

What about bench bleeding? Any good tips there?
Title: Re: Please, help me bleed my custom brakes.
Post by: teazer on May 11, 2019, 00:24:08
The upper caliper will still have air in it at the top.  That caliper has to be removed and rotated so that the bleed nipple is above the rest of the caliper
Title: Re: Please, help me bleed my custom brakes.
Post by: irk miller on May 11, 2019, 01:59:25
Try filling the calipers from the bleed nipple ports with a syringe. 
Title: Re: Please, help me bleed my custom brakes.
Post by: J-Rod10 on May 11, 2019, 04:50:29
Back bleed them. Force fluid through the caliper to the master.

Looks like it's on upside down. Bleed nipple should be at the top, no? Air doesn't sink.
Title: Re: Please, help me bleed my custom brakes.
Post by: imwastefull on May 11, 2019, 07:04:06
Back bleed them. Force fluid through the caliper to the master.

I tried that

Quote
Looks like it's on upside down. Bleed nipple should be at the top, no? Air doesn't sink.

Not upside down - on the wrong end. These are front calipers that I'm adapting
Title: Re: Please, help me bleed my custom brakes.
Post by: imwastefull on May 11, 2019, 07:05:18
The upper caliper will still have air in it at the top.  That caliper has to be removed and rotated so that the bleed nipple is above the rest of the caliper

I think that's the ticket. I'm going to try and bench bleed it tomorrow
Title: Re: Please, help me bleed my custom brakes.
Post by: Jimbonaut on May 11, 2019, 11:38:01
Damn man that's a great looking ride - that exhaust looks killer. 

I had a similar problem on my KLR - no matter what I did I could not get an pressure in the rear brake.  I rebuilt the master cylinder but after forever long I realized I fitted the cupped washer on the piston in the MC the wrong way round.  After taking it all apart a hundred times I finally spotted this mistake - flipped the washer the correct way round, rebuilt everything and it worked just fine. 

Did you rebuild the MC or is it brand new?  Might the cupped washer be your culprit?