Spongy front brake - Can each component be tested?

[kiwiz]

The front brake on my Z1000J had always been spongy and no amount of bleeding fixed it.

As a result I decided to refurbished the front mastercylinder inserting the new piston assembly (the only part I have been able to buy in NZ at a price close to those overseas). This was after I had the cylinder bore checked for scoring by a brake shop.

However I have found that once again the brake remains spongy so I am wondering if its possible to test each compoment in the brake line individually?

For instance I put a blank bolt into the mastercylinder outlet and pulled the lever: it was rock solid. Would it be valid to assume that the MC is okay? If I test each length of hydaulic hose in like manner, looking for the sponginess to return should I be able to gradually work towards the faulty component?

It seems very extravagant to throw out all the hoses etc. on the basis that probably only one needs replacing.

Is there a better way of approaching this problem?

[Ed Z1-R]

Kiwiz,ok we see M/C is rebuilt works ok.
How old are the brake lines?
The best way to go is a set of stainless braided, you can make these up yourself.
Extravigent? Life is priceless.
Or try....
Firstly bleed the brakes until theres some pressure,then in turn bleed every banjo bolt connection from M/C down to calipers.
Squeeze lever,loosen bolt,it squirts,tighten bolt.Pump pressure and again hold in lever loosen/tighten banjo bolt until its just fluid.Work yer way down,then its the final bleed process.
Should work.

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[kiwiz]

Ed,
thanks for the reply.

I must admit my test on the MC suggests that the rebuild is okay. Absolutely rock solid when pulled into handelbar.

The hoses may be the originals. certainly I have not replaced them since I bought the bike in 1995. One of the lower pair is a bit strange in that it has a rubber sheath over the line. It looks to me as being a non standard replacement at some time. I suspect the upper and one of the lowers are the originals which would make them 25 years old. However I could not see any ballooning of the hoses when pressure ws applied, or is that barely noticeable?

I replaced one of the slave piston and caliper seals some time ago on one caliper which was sticking on but have left the other as it was.

[Steve R]

Kiwi,
Dont muck about!!!!
Replace those brake lines Now, you wont necessarily see them balloon, But 25 year old rubber Brake lines are not safe at all. Put stainless braided on or if its concours new standard ones, but do change them. Too few zed one lovers about to lose one!
Regards Steve

[Davy Doherty]

I agree with steve, don't take a chance it's not worth it,, Look at my signature!!!

[Big John]

Kiwi,
All my recent Zeds have had braided hoses of one sort or another fitted and the improvement over stock is pronounced.

[BShaw]

One other thing. Not sure about J brakes but on some bikes the bleed nipple isn,t at 12 oclock, so will never get rid of all the air. its more than likley that the hoses are shot as previously said but thats my two penny worth...... Baza

[hanskloss]

I went braided way on my Z900 and the gain is so obvious, I'd say you get 40-50% more brakes , my genuine hoses are made in 1975 and they work OK if you bear in mind you're riding 30 years old bike/design, remember these are heavy bastards and back than the brakes were state of the art but obviously things have improved over 30 years and now they're as good as on pizza bike

[Ed Z1-R]

25 YEARS OLD! :

Bin them :


If you not brave to DIY,get a company to make them,theres many.
You could try Goodridge,Exeter,UK.

Deal with them direct,if need be send them the setup youve got.



P.S. Stainless is the way to go

:

[kiwiz]

guys,
talk about speaking with one voice! Yes I have ordered 3 new braided hoses from a local specialist brake shop. Cost around NZ$60 (pds20) each and should be ready mid week.

No one has commented on my "test" process for the components. Given that I have rebuilt the MC myself, I was a little concerned that it was another less than perfect DIY job. It seems logical to me that if I blank off the banjo bolt hole with a plain bolt, and squeeze the brake with no sponginess evident, then the MC is fine?

I still have not overhauled one of the two calipers. I did the other because of disc drag which I found was due to corrosion of the slave piston, but I have left the other alone (so far). I think any corrosion in the caliper is unlikely to cause sponginess. Yes the nipple is towards the top of thr piston bore which makes me think its reasonably efficient in collecting the air.

[Ed Z1-R]

i would say its ok but try the banjo method as described.To rebuild the M./C is straight forward job.As long as the bore was fine should be ok.
Thats not a bad price for the lines what type are they?

[Jeff Saunders]

on some of the bikes, the only way to bleed them is to remove the caliper from the forks. Kawasaki sure was dumb with a few models (KZ900 LTD for example)...

[kiwiz]

Ed,
the lines are being made now and hopefully turn out to be braided stainless with swaged fittings. We will see later in the week. They shop said about NZ$60 each which equates to 20PDS in real money.

[kiwiz]

This is what NZ$187 buys down under: 3 swaged stainless hoses

[kiwiz]

guys,
I have installed the braided hoses and bleed it per instructions however the lever still seems spongy and a road test confirmed the poor braking. (yes the old girl is mobile again)

I have been very careful in checking the fluid exiting the bleed holes and I cannot see any bubbles in it. I have notice a slight dampness (definitely not drips) of fluid at the banjo fittings but the bolts seem tight enough by hand (frankly I am terrified of shearing them off; 22ft/lbs seems a pretty high torque for a hollow bolt)

However one thing did surpise me was the fountain of fluid in the MC when the brake was applied. because the lid was off the MC for top up purposes every time the lever was applied fluid seemed to jet upwards from the LH hole (see photo) I was surprised to see that as I would have expected for the brakes to work the no fluid should escape into the reservoir on the compression stroke, and it should be sucked in upon lever release? Does anyone know if what I am seeing is normal?

Its quite possible I have made a mistake on reassembly of the MC as I fitted a new piston kit