R6 front brake issues

[scoot]

Hey all,I've got a strange one for you.

I recently fitted Goodridge lines to my bike and had a bastard of a time getting fluid down the lines. But now the front brakes have a intermittent problem.

After repeatedly bleeding the front, the brakes feel spongy one time then the next time I take my bike out they feel great. It feels like there's air in the system but each time I've bled them there's been no air in the lines. It's got me thinking,could it be time to put a seal kit through the master cylinder? It's got me stuffed.

Any help or advice would be a great help.

Cheers

Scoot

[roadracer]

What year is it?

Standard Master cylinder?

Could be a number of factors;

Is the brake fluid new(what brand?), from a freshly opened bottle?

How old are the pads and what type/brand/wear do they have?(they might only be "good" when the temperature's up..)

Calipers could need a clean

Pads could be slightly glazed

Could more-than-likely still be an air pocket in the system. You can almost reverse-out any trapped air bubbles by squeezing the pads back in the calipers, then crack the master cylinder banjo with slight pressure on the lever while you undo/retighten it.

Could also be the case if you re-used old copper washers

Sometimes even a properly bled lever can feel "squishy" if the pads are shot, because normal lever pressure does not=good bite.

[scoot]

What year is it?

Standard Master cylinder?

Could be a number of factors;

Is the brake fluid new(what brand?), from a freshly opened bottle?

How old are the pads and what type/brand/wear do they have?(they might only be "good" when the temperature's up..)

Calipers could need a clean

Pads could be slightly glazed

Could more-than-likely still be an air pocket in the system. You can almost reverse-out any trapped air bubbles by squeezing the pads back in the calipers, then crack the master cylinder banjo with slight pressure on the lever while you undo/retighten it.

Could also be the case if you re-used old copper washers

Sometimes even a properly bled lever can feel "squishy" if the pads are shot, because normal lever pressure does not=good bite.

Hey roadracer,

It's a 2001 with standard master cylinder,

Brand new Motul dot 4 fluid

The pads came on the bike not sure of brand but have a GG marking and have heaps of meat on 'em.

Everything was all good until I changed the lines,used the new copper washers and banjo bolts that came in the kit.

I've bleed the system twice including the master cylinder but to no avail.

What's got me stuffed is that the feel like crap in the morning but after I knock off work they feel awesome on the way home or vice versa.

[roadracer]

The pads came on the bike not sure of brand but have a GG marking and have heaps of meat on 'em.

Everything was all good until I changed the lines,used the new copper washers and banjo bolts that came in the kit.

I've bleed the system twice including the master cylinder but to no avail.

What's got me stuffed is that the feel like crap in the morning but after I knock off work they feel awesome on the way home or vice versa.

GG is the friction rating of the pad, GG's are a great street pad so I can't see them being the issue. Most new sportsbikes have "HH" ratings in the front which work better at higher temps reached on track/very fast road etc.

Try mounting a zip-tie around the brake lever to the throttle-not heaps of pressure, but just enough to give resistance in the fluid. Turn the bars so the master cylinder is at the highest point. Leaving the system pressurized like this, overnight, means the temperature change will bring the bubbles to the top where they are harmless.

If that doesn't work, you might do with a caliper clean and master cylinder rebuild, but I'm fairly certain it's still air in the system given your circumstances.

[rossm]

To test if it's the m/c if you squeeze the brake lever and you at first get good pressure but as you hold it on the lever then heads for the bars, that's your m/c seals gone.

*edit* cause I should learn to spell

[Ascalon]

I found a good technique that seems to reduce the number of variables in sorting out these things.

Castrol Red Rubber Grease is compatible with the hydraulic and dust sealks on bike brakes.

Whip off the caliper, remove the pads and pump out the pistons. Clean the xposed areas and then coat with a smear of red rubber grease. Push them home and pump them out again a few times. Do this all round and bleed again. You might find that the problem is sorted.

However, before you do any of this try this:

With the front wheel in the air and able to spin freely, pump the lever three times, as if bleeding, and then hold it for ten seconds.

Then let the lever go and see if the wheel spins easily. If not, you might ahve a sticky piston somewhere. That may be your problem. The red grease will osrt it out too.

A