Topic: Brakes refuse to be bled?!

[Hush]

CB650Z twin front discs, I've just fitted new seals to one side as it was leaking, now cannot get brakes to stay bled!?
The discs seem to have bled off fine at the wheels but I'm still getting very fine bubbles at the master cylinder.
I was trying a different way of bleeding the system to what I would normally use, I think TT put it on the forum, using a long tube and letting the system self bleed--this worked fine but still the very fine bubbles at the master cylinder and the lever feels decidedly soft, I wouldn't trust it on highway riding.
Any bright ideas or suggestions except from Marti as he will just want me to weld something to the handle bars or such.

[Hush]

Just me here in Cyberspace huh, well I've decided to let the beggars bleed all night to see if that has any effect, failing that I intend to take her out and do some white knuckle stops and see if I can shake something loose.
In a more practical state of mind I would probably order a new master cylinder kit, no actually I have replaced the old one already so scotch that idea!
Ah stuff it I'm going to bed ZZZZZZZZZZZZZZZZZZ

[rklystron]

I know this is not going to help you any. When I did the front disc brakes on my F2 it took me 2 days to finally get rid of the micro bubbles in the system. These bubbles need to be expelled or you brakes will be mushy and undependable as you described. I finally broke down and picked up brake bleeding kit. This helped some. I know your pain on this. I have enclosed a pic of the kit I described. Perhaps this will help.

I wish you the best!

Scott

[Hush]

Cheers guys, I like the idea of fitting something to the lever Fishhead, I did notice that when I applied the lever the "micro" bubbles kept arriving so will give that a go.
Thanks for the tip on the micro bubbles Rklystron, I have not encountered this before on any of my other bikes.

[goon 1492]

Pm hondaman he described this in another thread in this last week, called it the brake bleed torture test or something like that.

[eldar]

Did you clean out the master itself at all? Those things crud up pretty good. It may be possible that the seals in there are going out and letting in a small bit of air too.

I have seen this. Never enough fluid came out to notice anything but there were always little bubbles.

[rklystron]

There are 2 holes in the master cylinder. 1 is for the supply and the other the return. Your return could be plugged. This happened to me due to bead blasting the master cylinder. I had to drill the return orifice. Big pain in the rear end. to say the least. Make sure both holes are open.

[eldar]

Well that generally does not generate bubbles but it will prevent the cylinder from retracting!

[rklystron]

In my case bubbles were being expelled from only from the supply side. Nothing was coming from the return side. If he is seeing bubbles from the return orifice I would say that side is probably alright. The generation of bubbles was from air being in the line and had nothing to do with the clogged return line. Since bubbles could not expel on the return side they somehow migrated to the supply side. Just something to think about. I happened to me is all I am saying.

Scott

[eldar]

No I certainly under stand it. Air gets trapped all over the place in these systems. I just had not heard anyone have that happen.

[Hush]

Its coming right, just patience and more patience.
The trick with the rope helped I think, my lever is now a lot firmer.
I had to dump all the fluid from the master cylinder when I did the discs so I should have expected some air in the top area too.

[rklystron]

Outstanding. I am glad to hear you are making progress.

[jsaab2748]

I know this is not going to help you any. When I did the front disc brakes on my F2 it took me 2 days to finally get rid of the micro bubbles in the system. These bubbles need to be expelled or you brakes will be mushy and undependable as you described. I finally broke down and picked up brake bleeding kit. This helped some. I know your pain on this. I have enclosed a pic of the kit I described. Perhaps this will help.

I wish you the best!

Scott

 Some automotive bleeding kits allow the user to bleed the system in reverse, pressurizing fresh fluid from the reservoir of the tool, and forcing it up thru the entire system backwards. The tool is attached to the caliper bleeder screw, and you start with a dry master cylinder. Not that this helps your situation, but if you have the tool, it takes about 30 seconds to completely bleed a single caliper sohc brake system. I did both my bikes like that. Just gotta make sure you do things sowly, or you end up with a fluid stream from the master return hole that hits the ceiling, as the master cyl. fills.
Don't ask how I know this

[Bodi]

You can reverse bleed the system without any extra tools. First loosen the two big attaching bolts on each caliper till only a couple of threads are engaged. Pump both caliper pistons out about 3/4 of an inch each - you don't want the pistons to drop out but you want a lot of fluid in the cylinders. You will have to fill the m/c reservoir as you pump the pistons out. Screw in the big bolts until the pads just touch the disc. Now bleed each caliper as normal - that expels any air bubbles that have been pushed in.
Leave the bike overnight allowing whatever air is in there to float up as high as it can.
Next day screw in the bolts on the calipers again. You will have to remove brake fluid from the reservoir as you do this or it'll overflow and dissolve your paintjob, so OK I lied you will need a tool of sorts... I have used a toddler oral medicine syringe (any drug store has these if you don't have small kids and a collection of syringes).
This flows the fluid up - the way the bubbles like to go - to the reservoir and takes a lot of air out.
The Honda system has the switch tee and a dual system usually has another tee - these have a strong tendency to trap bubbles. Going to a hose system with single lines from the m/c (with a long banjo bolt) straight to the caliper eliminates most bleeding problems. You can use a switch banjo bolt or a modern m/c with integrated switch to eliminate the pressure brakelight switch.

[ThomasTedder]

Get a vacuum bleeder. No kidding, I can bleed any brake in about two minutes flat with a very firm feel. I use the mightyvac. I think I paid about $30 for it at autozone. It's probably the best tool I have. Just hook it up, apply some vacuum, and open the nipple. Make sure to keep the resivoir full. This is the only way I have ever been able to get a motorcycle brake bled (not to mention the slave cylinder on my 4Runner, which is why I bought it in the first place)

[eldar]

It is odd but I do not have to do any of this stuff to get my brake to bleed out. Make sure you all are cleaning out the caliper very well. DOT3 fluid causes a lot of white crusty buildup inside the caliper and that can cause air leaks as this crud gets under the seal and then the seal does not work very well. Also make sure the seal is good too.