Brake bleeding problem??

[paddlesat16]

Hi guys

Bike=cb250nb Superdream 1982
it had no problems before I rebuilt the braking system, except thirty year old braking system.

First off I have rebuilt the brake master cylinder with new internals, new reservoir cup and seal, replaced the brake line with a stainless steel goodridge jobby, new bleed nipple, I have left the caliper alone for the moment.

The problem is the system won't bleed now, I have replenished the fluid etc, following all the brake bleeding techniques from off of here and u-tube videos. I cannot get a hard(harder) lever what so ever. I have back filled etc but to know avail.

I do notice though I seem to get micro bubbles when I bleed, this to me indicates I have a leak somewhere.

what do yah reckon? One of the seals?
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I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T.

[Kickstart]

Hi

I would strip and rebuild the caliper first.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Howling TerrorOutOfOffice]

I have a very similar (if not the same) brake system on my bike.
Replace your banjo washers if not new.
Think you may of answered your own question regarding the seals.
I replaced mine and the dust seal. Also the sealing band on the lower bolt. Oh..and the rubber boots on the bracket.

*I found that reverse filling then doing the 'pull lever almost to bar then close the bleed nipple' way worked.

*Long version

Fill reservoir-spanner on nipple- tube on nipple - tube submerged in a pot of fluid.
Rag just in case tube pops off.
Pump lever to build pressure and then simultaneously start pulling the lever as you loosen the bleed screw. Before you reach the bar close the bleed screw. Watch the air get pushed out. Repeat a few more times then tap the banjos and lines. Keep going until no bubbles get pushed out.
Takes up to 10mins from a completely empty system (reverse filled via a syringe)

If you do strip down the caliper etc keep everything really clean.

Let us know how you get on.


Pat
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[fiery tupp]

It could be air behind the piston ? push it all the way in & clamp it for a while & bleed with it in first then release & continue , I have done this before & ok so maybe worth a try eh .....R
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If you can't fix it with a hammer , use your head .

[paddlesat16]

Hi guys

Thanks for all the reply guys,

First off the banjo's and washers are new they came with the goodridge hose.

Keith: I have left the caliper till funds reappear, superdream should be renamed money pit...

Pat: I will try your techniques as described, over the weekend when more time allows.

I was advised last night by a mate to clamp the lever and leave it overnight, this will show up any leaks at the joints.

I will post more when more progress is made.

Cheers for your combined help guys
____________________
I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T.

[Kickstart]

Hi

Main place for leaks are the seals. You have replaced those in the m/c and also the sealing crush washers, hence why I suspect the one remaining set of seals (ie, the calipers seals) and the ones to check.

In the short term pump the piston out, take the seals out and clean up behind the seals. Check the seals carefully. Many people reuse seals.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[paddlesat16]

Update time:

So I had no joy with the master cylinder at all, more of the same(micro bubbles in the fluid) but I couldn't find the leak. I suspect the new O-Ring between the fluid cup and master cylinder.

I decided to replace the master cylinder in the end with an item from wemoto, hence even more poor now. Amazingly quick service, I ordered in the afternoon and it arived next morning.

Good news

Fitting new brake master cylinder 10mins
filling cylinder with new fluid and bleeding probably another 5 mins
and instant hard lever.
____________________
I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T.

[calyx]

[Dazbo666]