Another thread about brakes (I know!) - help please!

[alun111]

I've recently rebuilt the rear brake caliper on my 1993 bandit 400.

I did this after I re-insured the bike after it being stood for 6 months. I took the rear caliper off because the brakes were squeeling when I pushed the bike backwards - my initial plan was to clean the pistons and push them back in, but they turned out to be completely seized as well as the pad pins.

So I decided to take the caliper off and get the pins and the pistons out and give everything a clean and re-assemble. I did so successfully. I bought brand new pistons (stainless steel) and made the pad pins myself. The old seals were intact and in good order so I cleaned them up and on re-fitting coated them in brake fluid. I also thoroughly cleaned out the grooves that the seals sit in with brake fluid and a wire brush to get rid of all corrosion.

On re-fitting the caliper to the bike I had to fill the reservoir about 7 or 8 times whilst I was bleeding (also changing the fluid at the same time).

Now, Sorry for the long post, but I wanted to give you all an idea of the history.

To the problem - my rear brake pedal has a lot of travel. It seems like there's a lot of movement also before the brake starts to do anything. To take the pedal to the end of it's travel I have to take my foot off the peg and use my toes!

My guesses are either the rubber brake hose is old and it's expanding too much, the master cylinder needs a rebuild, or I didn't bleed the brakes substantially. Either way I'm losing pressure somewhere, and would appreciate it if you guys could give me ideas you have.

Oh, and there doesn't seem to be any leaks.

Thanks guys and girls.
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Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[The Artist]

id say brake needs bleeding again, especially after a rebuild.

Then master cylinder needs stripping down and a good going over if bleeding doesn't fix it.

[Frost]

Bleeding may be the issue and is easily solved with a long length of clear pipe on the nipple.


There will also be a rod running to the cylinder, this may be adjustable and will solve all your problems if so.

[NiteMare]

and if none of the others have given you the correct answer i suspect you didn't get the seal seats as clean as you thought ...

and the seals are still gripping the pistons and drawing them back into the caliper body when you release the brake pedal ...

when cleaning calipers (strip and clean) i use a small piece of bent metal to scrape all the corrosion out of the seal seat, two reasons for doing it my way ...

first being you can't see into the seat properly, so you can then "feel" for corrosion..

second being that the corrosion is generally pretty hard, the metal can be used aggressively to scrape it out ...

i then lube the seat with brake fluid and fit new seals then lube those and gently push the pistons back in (after cleaning of course)...

as long as the pistons aren't damaged i just polish those with solvol
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it ain't broke...

i ain't fixed it enough

[alun111]

NiteMare - I used a small tooth brush sized steel wire brush to clean the grooves where the oil seels sit, I thought i'd done a pretty good job of it, the seals clicked in to place nicely and i had lubed them with brake fluid all over. They seemed to sit right.

You're theory sounds about right though with the seals gripping the pistons and pulling them back when the pedal is released - this would mean you'd have to press the pedal further to do the same job as the pads wouldn't be already be skimming the disc - am I right?

DaFrostyOne - About the "rod"going into the master cylinder - I thought that you could only adjust the brake pedal height by this? The brake pedal has only got a small amount of play before it gets "springy" so to speak.

allymoss - Does it take more bleeding after a caliper rebuild? I thought 7 or 8 times would have been well enough.
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[The Artist]

after I do a rebuild, I bleed them then after a few days do it again. Gives it a chance for everything to settle in, heat up and shift any air bubbles around. You shouldn't have to do it a third time.

But before you do anything, check the little bar going into the master cylinder is not loose and needs adjusting! Will save a lot of hassle.

[NiteMare]

[alun111]

I'll give bleeding another try, and then I'll resort to caliper apart again then. I know someone with a vacuum bleeder so i'll try that.
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[Vincent]

Are you sure you're bleeding it right? Does the brake get harder after you pump the lever vigorously about 10 - 20 times? If it does, you've got air in there still. Don't release the bleed nipple until you've built up a bit of pressure by pumping the lever and keep the lever pressed down until you've tightened the nipple up again. Hope this helps.

[Kickstart]

Hi

I would say that 90% likely the brakes still need bleeding. There will probably be 2 bleed nipples on the caliper (if it is a standard quick seize Suzuki caliper), one for each half of the caliper. You need to bleed it using both of those (do one then the other).

All the best

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

[steve32]

i had the same prob when i did the rear brake on my gsxf there was to much travel on the leaver and i was on for a few hours trying to work it out and it came down to a small rubber washer that sits inbetween the twohalfs of the calliper it was perished and it was letting air back into the system and when i replaced it they bled and worked properly after that
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suzuki GSX 600F katana .: ~my bike up for sale~ :.
CBT = Completed
DAS= Working on it - theory test = Passed

[alun111]

Thanks for the replies guys, i'll definately try bleeding it again, and let you all know how I get on!
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70