Help: Brakes, brakes and brakes!!!

Hi,

I have a spongy brake lever problem that is driving my nuts. I know i know before throwing me rocks and say there's tons of topics how-to in this forum read my post ...

Model: GPZ 750 '82

The problem started when i changed the fluid for the first time since i've bought this bike. (fluid never have been changed in 28 years!!! )

I could never achieve a firm handle as it was. Tried Gravity bleed,traditional bleeding (kawa manual), fill from nipple with a syringe and zip tie overnight method.

Decided to take a look to the MC piston and oh boy it was FUBAR.Corrosion from everywhere (piston and chamber was almost dissolved)!
I've thrashed the MC and buy a brand new one from ebay (100$). I put it back with everything still original (lines,caliper seals) no improvement.

Bought new & installed Stainless Steel lines, crush washer and caliper rebuilt kit. Again no improvement at all still way too spongy (lever can reach easily the bar).

Here i am, asking for any advice looking at my 4 empty bottles of DOT4 (almost a gallon !!) fluid I've used during the last bleeding.


Best Regards,
Laurent

EDIT: I forgot to specify it's only the front brakes disc (2x) rear disc bleeding was piece of cake!

zip tie the lever to the bar overnight and just keep bleeding,they can be a real bitch some times

Does your bike have the anti dive valve under the triple clamps? Maybe air still in this. I also had some trouble with my 1000, make sure that when bleeding the master cylinder reservoir is at the highest position. Pump the lever up many times and hold it to the bars, then loosen the bleeder, close it before releasing the lever. Clear tubing hooked to the bleeder valve and put into a clear container of brake fluid will show you if any air bubbles come out. Be patient, It should come good.

Try to find someone with a pressure bleeder (tank type). You will need to use an old MC cap to make an adapter. Using the pressure bleeder you can push everything (old fluid, air, dirt, etc.) through the system without pumping lever or manipulating bleeders. Just hook up the adapter, open the pressure bleeded valve, and open the bleeders until clean bubble-free fluid flows. Then close bleeders an disconnect pressure bleeder. Done - 10 minutes. Ed

Here's what they look like (although this one is priced pretty high):

KD 2222

Yea the pressure bleeder is great but not in every ones budget. You can make one, if you get a old master cap, drill and tap it for a small hose fitting, get a jug that will hold pressure, and make it have a hose at the bottom for the out going fluid, even the head pressure from the bottle hanging above the Master will force the fluid through.
But a buy it now for cheap, is a CHINA copy of the famous Mighty Vac, you can use it to either suck the fluid or pressure the fluid through your system. Harbor Freight or Ebay, Good luck.

The hydraulic brake light activator switch (if it has one) can also hold air.

I made a pressure bleeder out of a garden sprayer for about $10. You can Google 'homemade pressure bleeder' and find plans. Works great. Another thing I discovered bleeding my KZ750; If the MC is tilted down, so that the lever end is up and the outgoing hose is down, it can hold air that even a pressure bleeder won't get out. Between moving the bars and repositioning the MC, get it as level as possible.

Does your bike have the anti dive valve under the triple clamps?

If you mean that piece of ^%$& fitting (i think there's alot air inside) that split the hydraulic brakes lines (MC to two calipers) then yes.

Pump the lever up many times and hold it to the bars, then loosen the bleeder, close it before releasing the lever. Clear tubing hooked to the bleeder valve and put into a clear container of brake fluid will show you if any air bubbles come out.

I did that so many times my fingers are hurting ! The problem is that sometimes the lever got a little bit firmer and then when i do open the nipple to bleed like you said the lever after that is more spongy than ever!

Also, there's no bubble going out but streams of tiny microscopic bubbles (like little foaming). Maybe my brake fluid brand sucks ? (Prestone DOT4)

zip tie the lever to the bar overnight and just keep bleeding,they can be a real bitch some times

Done that 3 times already and tied for 48 hours without touching anything!

Try to find someone with a pressure bleeder (tank type). You will need to use an old MC cap to make an adapter. Using the pressure bleeder you can push everything (old fluid, air, dirt, etc.) through the system without pumping lever or manipulating bleeders. Just hook up the adapter, open the pressure bleeded valve, and open the bleeders until clean bubble-free fluid flows. Then close bleeders an disconnect pressure bleeder. Done - 10 minutes. Ed

Because it's been one month of bleeding madness, i think it would be good to buy one but i'm confused what could be the best , vacuum or pressure bleeding (vacuum sucks the air out of the system instead of introducing it with pressurized bleeding no ?

The hydraulic brake light activator switch (if it has one) can also hold air.

I don't have this mechanical switch on my MC.

Here's the picture of it.

Another thing I discovered bleeding my KZ750; If the MC is tilted down, so that the lever end is up and the outgoing hose is down, it can hold air that even a pressure bleeder won't get out. Between moving the bars and repositioning the MC, get it as level as possible.

You know i never thought of that because many forums they say to make your MC at angle (lever tip pointing at sky) to get the bubbles out by gravity through the MC relief hole.

ELCouz wrote: "Because it's been one month of bleeding madness, i think it would be good to buy one but i'm confused what could be the best , vacuum or pressure bleeding (vacuum sucks the air out of the system instead of introducing it with pressurized bleeding no ?"

A pressure bleeder will not introduce air into the brake system. The bleeder tank can hold about 1 gallon of brake fluid. The top and bottom of the tank are separated by a rubber diaphram. The top of the tank holds the brake fluid, the bottom holds the air pressure. You fill the top with fluid with the air valve open on the bottom (zero air pressure) then you close the top (fluid) valve. You then pressurize the bottom of the tank with about 20 PSI of air (there's a pressure gage on the tank - even 10 or 15 PSI works fine). The brake fluid hose is attached to the top of the tank so when you first open the brake fluid hose valve any air that was left the top of the tank when you filled it is forced out as the diaphram pushes up on the fluid. From that point on there is nothing that can come out of the hose except brake fluid. Even if you let the whole gallon come out there is no air in the top of the tank to get in your brake system. One word of caution - when finished, before removing the hose MC adapter open the air valve on the bottom half of the tank to relieve the pressure THEN close the hose valve, then remove hose from adapter. Otherwise (and I can show you this under the hood of one of my cars) you will squirt a shot of brake fluid out of the adapter. This isn't a problem if the air pressure is relieved first. Ed

just for the sake of curiosity 650ed, what brand and model of pressure bleeder you have ?

I have a KD 2222. My wife got it for me (after I picked it out) about 10 years ago for Christmas because I have 3 cars a truck and the bike. I flush the brakes on them all every other year. It cost considerably less when I got it (around $130) than the prices I see now, but you can still find them for less than $200. Here's one example:

KD 2222

If you have multiple cars/bikes to maintain or if you can go halfs with a friend who maintains his own vehicles the pressure bleeder is worth the bucks. It's nice not to have to have someone pumping the brake pedal on the car while you manipulate the bleeders and worry about the master cylinder running low on fluid. (I think that's why my wife was willing to buy it for me.) There are other brands. If you buy one just be sure that there are separate chambers for the air and brake fluid. Some simply pressurize a tank with the air and fluid together. This can lead to the moisture in the pressurized air being introduced to the brake fluid - not good. If you get one let me know and I can give you some tips on making the adapter for your bike. Adapters are available for most cars, but I didn't find any for bikes. Ed

I have received my speed bleeders today.

Now it's better (still spongy stops at 1/4 at the handlebar) but I've realized that after too many pumps (+500) i may have aerated the brake fluid! I will tie-wrap the lever at leave it overnight and continue tomorrow.

I will keep you in touch guys!

Also I will try another brand of dot4 fluid.

On my current brand (Prestone) it says fully synthetic. I never heard of dino brake fluid . I think they are all synthetic!