Soft brake trick - damaging?

[90s]

The brakes on my GSX are not the best, although they are OK. This is generally accepted. However, mine "get soft" fairly regularly. No fluid is being lost from the system, and there is no problem that I can see.
Last service my bike shop mechanic used heavy rubber bands to pull in the brake lever, and left it in the workshop overnight. He said that this bled the air out of the system gently. Since seeing this trick I've being using a cable tie every few weeks to do this over the weekend.
Sure enough, come Monday morning the brakes are firm again.
A few weeks later and the mush is back with a vengeance.
My first question is:
1) can this trick being used regularly damage the system in any way - too much pressure on the seals etc?
2) any ideas of how to improve the situation - is this a poorly sealed master cyclinder or something?
3) any other advice?

Thanks in advance for your ideas

[vifferman]

I had this same problem on my VTR1000 - they're renowned for it. In that case, the problem is that the brake lines splits in two, and has a 'hump' above the front mudguard. This 'hump' collects air bubbles and is hard to bleed. Like you, I did the "tie the brake lever up overnight" trick, but it doesn't really help. It just forces the air bubbles back into solution in the brake fluid, then eventually, they bubble out again.

What I did in the end was overhaul the brake calipers (not the real problem, but it helped) and fitted dual brake lines (braided) to the front brakes.

Problem solved.

I suspect that in your case, you've got somewhere that bubbles are collecting: a banjo connection or other fitting. It's possible you've also got something like a worn seal allowing air to slowly leak in, but not that likely.

[Pwalo]

Does your bike still have it's original brake lines? These can get soft over time, and it may be a good (but messy) idea to replace them. You can go the braided lines route, but that's probably not necessary unless you like to push on a bit when you're riding.

[vifferman]

Does your bike still have it's original brake lines? These can get soft over time, and it may be a good (but messy) idea to replace them. You can go the braided lines route, but that's probably not necessary unless you like to push on a bit when you're riding.

Just a comment on that - when I went to braided lines, there was no performance improvement (why would there be?) but there was much better feel at the lever, and no mushiness.
However, some braided lines can feel a bit 'wooden' compared to OEM; the second set I had on the VTR weren't as good as the first ones (unfortunately, not legal) and did feel a bit wooden, Still HEAPS better'n the OEM ones.

[Pwalo]

Just a comment on that - when I went to braided lines, there was no performance improvement (why would there be?) but there was much better feel at the lever, and no mushiness.
However, some braided lines can feel a bit 'wooden' compared to OEM; the second set I had on the VTR weren't as good as the first ones (unfortunately, not legal) and did feel a bit wooden, Still HEAPS better'n the OEM ones.

The wooden feeling is exactly what I mean. Besides who uses brakes on a V twin?

[90s]

Does your bike still have it's original brake lines? These can get soft over time, and it may be a good (but messy) idea to replace them. You can go the braided lines route, but that's probably not necessary unless you like to push on a bit when you're riding.

I've got braided lines, fully dot compliant etc and according to Haldanes & Wild West well made. Basically line goes from lever and banjo to the split just above the front wheel then splits into two lines, one for each caliper.

The 'trick' DOES work for up to two week - so as suggested there is some air trapped in the junction?

[FROSTY:Me]

Before all this effort Id suggest getting the brake fluid changed and a propper bleed be done

[Max Preload]

Before all this effort Id suggest getting the brake fluid changed and a propper bleed be done

And failing that, in my experience, a full strip of the calipers to free up the pistons and restore lever feel.

[F5 Dave]

Vifferman has it, that pressure trick isn't long term. As Frost sez new fluid & proper bleed. You may want to consider a mc rebuild if that doesn't do the trick.

Pwalo. erm do V twin riders not like front brakes? Last time I checked the engine was connected to the rear via a chain. So how can you 'brake' harder with the rear than the front?

[xwhatsit]

Pwalo. erm do V twin riders not like front brakes? Last time I checked the engine was connected to the rear via a chain. So how can you 'brake' harder with the rear than the front?

Ride smoothly, you rough old 2-smoker

Engine braking is enough in most twisties for me, and we all know an ancient 250 single is totally the same as a 1000cc V-twin.

[F5 Dave]

Try speeding up a little.

So what is that circle thingy in the top rhs of your Avatar anyway? None of my copies have it.

[FROSTY:Me]

HAD a bit of a think about this.Memory being fecked and all that.
BEFORE changing the brake fluid on the bike using this lever back against bar trick does put the air bubbles in the lines back into the fluid making it easier to flush out when the fluid changes

[MrMelon]

My 600 was doing this. Swapping the fluid out and bleeding didn't fix it. I rebuilt the master cylinder ($50 for a kit) and my brakes feel as good as new again.

[xwhatsit]

Try speeding up a little.

So what is that circle thingy in the top rhs of your Avatar anyway? None of my copies have it.

Like I said, everybody knows 250 singles are just the same as 1000cc twins -- surely corner entry speeds can't be that much higher?

It just says

PINK
FLOYD
THE
DARK SIDE
OF THE
MOON

I got it cheap from Japan, perhaps that's the edition they got? Vinyl of course. Yay for EMS combined shipping.

[caseye]

Hi guys and girls is there anyone out there who can point me towards a shop/workshop that can replace my 1981 XV's front brake lines, they're at the age of no return. I'd like to ride it into a workshop and have the lines replaced either in rubber or braided, but so far I've not found a place that can do that.
Any help is appreciated.