soft brakes twin disc set up

I have a 1977 kz1000. I recently switched out from a single disc to a double disc set up. I think I got all of the correct parts from a motorcycle salvage. But I can't get the brakes to work right! There is no bite. I still have the original master cylinder which I know can affect feel. But I thought I would still have some braking. Am I just not bleeding them right??

It can be a real bugger to get all the air out.

If u havent already,Spengler makes a great set of teflon coated braided hoses.They are smaller inside diameter,easier to bleed, andgive great firm brake feel.bj

Even a tiny amount of air in the system will make them mushy.

dam10r wrote:

I have a 1977 kz1000. I recently switched out from a single disc to a double disc set up. I think I got all of the correct parts from a motorcycle salvage. But I can't get the brakes to work right! There is no bite. I still have the original master cylinder which I know can affect feel. But I thought I would still have some braking. Am I just not bleeding them right??

I still have the original master cylinder ---
There's a red flag in this situation.

Stock 1977 KZ1000 with single front disc has 14mm master cylinder (size of bore).
The m/c was enlarged to 5/8" for stock KZ models with dual front discs.

When converting from single to dual front discs, should also change to the correct larger size master cylinder.

Reportedly, using dual front discs with the smaller 14mm m/c produces a dangerously over-sensitive front brake prone to locking the front wheel in an emergency braking situation, which results in loss of control and going down.

In non-emergency braking, an overly sensitive brake may be voluntarily modulated.
However, in a severe emergency braking situation, reflexes take over to involuntarily apply maximum squeeze to the lever. Especially detrimental on wet road surface, leaves, sand, or anything less than perfectly clean and dry.

Just so ya know.

Good Fortune!

You mention that you have the original M/C. If you mean the one that was intended for a single disc then that is likely to be your problem. You will need an M/C with a larger piston to move enough fluid for the two calipers that you now have.

I'm not sure about the exact sizes on a 1000, but on the 550's that I'm familiar with the single disc bikes use a 14mm M/C and the dual-disc bikes use a 16mm unit. I would expect that you would find a similar difference on the larger bikes also. The correct M/C combined with some braided steel lines will give you the results that you were expecting.

I guess I type too slowly....Patton beat me to the right answer !!

Although seemingly logical, it's actually not about pushing enough fluid.
It's about the hydraulic leverages involved.

Kawasaki engineers figured this out when designing the hydraulic braking system, so the m/c would produce "ideal" fluid pressure, not too much and not too little.

A stock single front disc bike should have sufficient braking power to "squall" the front tire at maximum braking.

The second disc is not supposed to instantly double the front braking force. Which is about what happens when using the same smaller m/c on two discs.

Ask the guys who busted their butts when the front wheel locked up due to an excessively sensitive front brake.

Good Fortune!

Don't agree at all with that.
When I added a 2nd disc to my Z1, I had the MC bored-out to take the 5/8 service kit from the dual disced bikes.( still have it if anyone interested)
What a mistake, the lever was way too had with poor feed-back.
I then bought a 14mm MC that I completely rebuilt and have been using it for the last 10 years.
Much better lever feel and control.
As for being over sensitive that's total BS.
If you want to talk about over sensitive talk about newer bikes, like my ZRX 1100 or ZX12R where I can lock the wheel with a single finger.
with the Z1 I will have to pull VERY hard will all my fingers to do it

So if I keep the stock MC what is the best way to bleed the lines? I have done it many times, but can't get rid of the sponge. Thanks for all the other suggestions!

luc wrote:

Don't agree at all with that.
When I added a 2nd disc to my Z1, I had the MC bored-out to take the 5/8 service kit from the dual disced bikes.( still have it if anyone interested)
What a mistake, the lever was way too had with poor feed-back.
I then bought a 14mm MC that I completely rebuilt and have been using it for the last 10 years.
Much better lever feel and control.
As for being over sensitive that's total BS.
If you want to talk about over sensitive talk about newer bikes, like my ZRX 1100 or ZX12R where I can lock the wheel with a single finger.
with the Z1 I will have to pull VERY hard will all my fingers to do it

The braking system components are designed to function as a coherent unit, toward achieving ideal braking efficiency.

Among other things, this involves hydraulics engineering, with the matching and balancing of such things as lever ratios vs. m/c area vs. caliper piston area vs. rotor diameter/radius vs. tire circumference, etc.

With progressively less effort needed for equivalent braking force, sooner or later a toggle switch effect is reached whereby minimal effort results in front wheel lock-up (not a good thing).

Hence the growing popularity of anti-lock brakes for motorcycles (as long since used on automobiles).

Even the most modern motorcycle front brakes are designed as a balanced system to achieve the most ideal braking efficiency.

Then again, maybe the present and past engineers were indeed all full of crap. How dare they design a front brake incapable of being instantly locked up by the mere thought of baby pinkie pressure. Throw the bums out. And let's goof around with willy-nilly changing of the components. What's to lose - oops, don't ask that. Vote a stoppie-king for president. :laugh: :laugh: :laugh:

Just my 10 cents to stop on a dime. :kiss:

Good Fortune!

otakar wrote:

Even a tiny amount of air in the system will make them mushy.

Absolutely !

If you have bikes, and you do brake work, you will benifit ten fold from purchasing a Mighty vac bleeder kit ! Many times what I will also do is remove the calipers and while under vacuume, I will roll the caliper around in mu hand to try and expel stubborn bubbles.