Spongy Brakes

[Shuriken]

If I bleed the brakes, add fluid, bleed, etc., and the brakes are still spongy, what next? I have to pump them so they tighten up. Should I keep trying to bleed them? I can't see that they are leaking..

Another issue:
I bought a K&L rear master cylinder rebuild kit. Complete waste of money. The plunger did not even fit. It comes without one o-ring where it should be so you practically have to destroy the o-ring getting it around something too big. Then the plunger won't move up and down because it's too fat to fit inside the cylinder. Complete waste.

So I have a rear master cylinder assembly that will pump some fluid out while I bleed it but will apparently not pump enough fluid to make the brake piston move... Any ideas?

I could check the order of parts assembly... How does it go?
washer
tin cap thingie
spring
o-ring
plunger?

Ben

[ratbyk]

Spongy Brakes

Ben, for tips on rebuilding the master go to Tech Tips on the left side of this page. Click off Repair on the scroll down. Then, Master Cylinder rebuild. This will cover one of the problems you mentioned.
Next, when I did the masters on mine I also had a great deal of trouble bleeding the rear brakes. Discovered that if I removed the master from the bike leaving the rear line and push rod etc.hooked up from the bike, if I tilted the master to slightly different angles (like less angle) then when it sat on the bike I could bleed it by hand on the push rod. When in this new position it pumped up quite quickly. I believe the problem was air trapped inside the bore of the master in a position that would not allow it to bleed out. I have suggested this to other owners from time to time and it worked for them.
Lots of luck and be careful of brake fluid around your painted surfaces. It likes to eat paint.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[chevy45412001]

rubber lines

Stock rubber lines can also cause spongy feeling brakes.Stainless steel lines are the way to go.(stock lines are usually 20+ yrs old,and like to Xpand when the brakes are applied)

[Shuriken]

I'll check the brakes again, but I could not use the K&L kit. The replacement plunger was too fat. Waste of money.

I wish I could figure out why one of my master cylinders is not working. Is there a good microfiche available to show parts assembly order so I can double check?

Ben

[beechfront]

spongy brakes

my brakes gradually got spongy on me this year. so i bled the lines/new brake fluid. did not make any difference. still need to pump brakes twice to get good braking.

so am i looking at new lines or what? i've tried various tricks such as letting it sit for a couple days with pressure on the lines... no luck.

[randy]

Beechfront, try this.

Grasp the line tight with your hand and squeeze the lever. If you can feel the line swell, that's a tell-tale sign that your lines are bad.

Good luck

Randy

[ratbyk]

Spongy Brakes

If you have bled the brakes and really do not have anymore air in the system it is time for a rebuild kit. SS lines will help a bit but until you are getting positive immediate action from the master your brakes are going to be iffy.
Ken/Sooke

[sidecarKev]

Do me a favor and just try this tonite. Take a piece of rope and tie or bungee the brake lever as close as you can to the handlebar. Leave it overnight and tell me what its like in the morning. It has worked for me. Really it has!

[beechfront]

i tried that several times... once for 2 days.

[Shuriken]

I have spongy front braking.

I've asked about the front master cylinder for the 79sf before, but I can't ever find my previous questions. I've searched by my own member name and also keywords.

Before I replaced leaky front fork seals, they leaked and soaked the front brake pads with oil. I can't get them clean. They are fairly cheap and I don't mind getting a new set. That will help. I have tried bleeding them many times, too.

However, I still have a spongy front braking system.

If there is a NEW replacement master cylinder for the 79sf, I'd rather have one than try to rebuild the old one. Since I can't find my previous messages, I'll ask again:

What new front master cylinder will work on my 79sf (stock bars and lines) and where can I order it from?

Ben

[randy]

Ben,

Your problem may be your hoses. Are they originals? Grab one tight with one hand and with the other apply the brake. If you feel the hose swell, you've found a problem.

[andreashweiss]

Cannot help you out with the front brake problem but I still have 2 good used rear master cylinders that will be clean and not in need of a kit.$25.00 includes shipping. andreas

[xschop]

spongy brakes

galfer stainless lines will practically throw you off your ride if you install them and mash hard on the front brake lever....

[wingnut]

Worried

I have the same problems with the brakes on my SH. Has any one had problems with the MC kits from Parts & More? Both the front and rear MCs need to rebuilt and I don't want to get a kit that has a plunger I can't use and is missing an o-ring.

[Shuriken]

I'm not interested in rebuilding the master cylinder. I have tried that before and experienced parts nightmares. Why rebuild if there is a new part available?

So that's my real question. I can't remember if the partsnmore master cylinder works on stock handlebars of the 79sf. It doesn't seem conclusive that it works. It doesn't seem conclusive that it will sit level on stock 79sf bars. It doesn't seem conclusive that the angle of the reservoir makes a difference, or that the angle of the p&more master cylinder is wrong.

Yeah, I have stock lines on the bike. I am not aware of a bolt-on solution. So the stock lines will flex of course some. Unless the stainless lines are still available, I'm not sure I can replace lines anyway.

Ben