Topic: 79 CB650 front brake

[Scotiabiker79]

So I rebuilt the front calliper.  New piston and seals.   Went to put pads in.  Too thick.  I googled it and someone on another site had same problem. Solution. I sanded them down on belt sander.   Worked well

Now issue is I’m trying to bleed brake. Brand new front master cylinder.  Filled reservoir.   I have pressure in the handle and tried bleeder valve.  Nothing.   Repeated several times nothing. 

Any suggestions from anyone would be appreciated.   . 

[Stev-o]

There is a procedure to bleeding the brake system, first off be patient.  I typically pull on the lever two or three times to build pressure and while holding it, loosen the bleeder screw.  Repeat as necessary.

A couple of notes:

- Dont let the brake fluid run on your paint!  It will damage it.
- The brake lever should not be pulled all the way to the grip.
- To lesson a mess in the shop, I put a hose on the bleeder screw leading into a bottle.
- If you cant get all the air out of the system, tie the brake lever depressed and leave overnight.

Good luck!

[Scotiabiker79]

Ok cool.  I’ll zip tied the lever.   Should I open the bleeder valve too

[scunny]

leave the bleeder closed overnight.

[Scotiabiker79]

Ok cool thanks

[Alan F.]

Leaving the steering turned full left or full right alternately overnight may help too, unless one overnight does the trick.

[Scotiabiker79]

Cool thx again for info

[Scotiabiker79]

And no dice.  I did have the cover to the master cylinder and screws in and tightened.  Hopefully my bad for doing that.  Cover off now and repeating the process over night.  Hopefully works. 

Thanks again to everyone for all the tips. 

[Alan F.]

Did you spray some brake cleaner through your brake hose before assembling to make sure it wasn't blocked?

Rubber brake hoses fail 2 ways: externally that you can see, or internally that you can't see.

Also banjo bolts can clog internally as well and might need to be cleaned out.

Yes, leave the cap off the master cylinder. And protect the rest of your bike from brake fluid by covering it with whatever you've got.

Another tip is slowly and gently squeezing the brake lever, only about 1/4 of its travel. Do this a few times and watch for tiny bubbles to rise from the tiny holes at the bottom of the master cylinder reservoir.

[Scotiabiker79]

I didn’t stick a needle down the banjo bolt holes or brake cleaner.  So that’s likely my problem.  I’ll have to take brake fluid out and take hose off and try and free the line up.   All I did was blow air into it when doing the bike over.  Laziness on my part.  Honestly didnt consider the hose woul be plugged.  Rookie mistake. 

[Alan F.]

If it's an original hose to the bike you may not be able to free the blockage. The inside of rubber brake hoses fail in such a way that the inner layers of tubing swell and block the line. At that point it's a replacement only situation. The one I had that had failed this way was stuck solid, I could pump the master cylinder but could feel the rubber line expanding with my hand on it, no brake fluid coming out the other end. (I had the problem you describe, with no brake fluid coming from the bleeder, so I took the line off the caliper first, no brake fluid in the line. After disassembling I later tried to shoot brake cleaner thru the line but it just came right back up from the end I sprayed into and sprayed my ceiling)