Front brake fluid change halp (Kwak ZR7-S)

[NJD]

Evening, morning, afternoon.. all the aforementioned and more.

More mechanical tasks, the joys.

Front brake lever on the Kwak is far too spongy so I'm going to bleed both calipers and see how much that does or doesn't improve performance. Couple of questions before I attempt (since I've only done the rear and that's a more basic set up):

(a) Is there anything to know about bleeding the front brakes before doing it (ie: how to avoid rounding of the screws in the fluid resivour .. as I've read that's common)

(b) Do I need to do one caliper first or just whatever one takes my fancy and then the other?

(c) I assume that once the fresh fluid starts flowing through the one caliper I can then, providing there's no air in the tube coming through with the fresh fluid, tightening it up and then start on the other caliper?

(d) Once both calipers have no air coming out of tube and fresh fluid flowing through keep pumping the lever until firm and then a ok to go for a test run straight away? (I've seen or read people cable tie'ing to bars and leaving overnight)

As I say I've done the rear not so long ago but just want to ensure I'm not missing anything since the front is a double setup although same calipers and brake lines etc so shouldn't be troublesome at all.

.. Further investigation may be needed after fluid change given how useless they are. Dangerously ineffective to the point not riding the bike is the safer option. Got the time to look the brakes over and change the fluid so see what fun awaits me.

Plan to leave the calipers in place and bleed then ride so should be less work than last time (the rebuild on the rear).

Oh, finally, the fluid below is OK to use? Had Halfords try to sell me car fluid at first then the wrong type when I ordered online and then gave me a different coloured bottle to the one I ordered. Reviews on Amazon state used on R6 and a Honda so should be fine, right?

https://s12.postimg.org/opxfb7sb1/castrol.jpg

Cheers all.
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The do it all, T̶h̶e̶ ̶b̶r̶o̶k̶e̶n̶ ̶o̶n̶e̶,̶ ̶T̶h̶e̶ ̶b̶i̶g̶ ̶l̶u̶m̶p̶,̶ ̶C̶h̶o̶n̶g̶ ̶N̶o̶o̶d̶l̶e̶

[sickpup]

So what's the difference between car ans motorcycle brake fluid?

[Kickstart]

Hi

I would doubt fluid alone will stop the brakes being spongy. Old fluid will get water in it will mean they can get spongy with heat (as the water boils). Air can get in there, but generally over time will work its way back out slowly. More likely the calipers need a strip and clean.

I tend to do each caliper and then repeat.

M/c screws can round off. Chances are they are JIS screws and most people do not have a screw driver for them and instead use a Philips one which contributes to the issue.

Car fluid and bike fluid are the same. There are some specialised fluids (eg, some race fluids have a low DOT rating as despite a high dry boiling point they have a low wet boiling point - great on track when the fluid is changed every meeting or so, useless on the road where the fluid gets changed very occasionally).

All the best

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

[NJD]

[wr6133]

Those Tokico 4 pots are famously spongy. I had the same on my ZZR and ended up binning them for a set of nissins. They are good for about 10 minutes after a rebuild and bleed and then just get spongy again.

[NJD]

[sickpup]

Are they spongey in use or only when stood still?

[wr6133]

[NJD]

[Baffler186]

I've had 2 pot tokiko's on my last two bikes, never had a problem with sponginess, however I did fit HEL lines to my Fazer. How old are the brake lines? And do you know when the brakes were last serviced?

If I were you I'd order new seals. If you're taking the calipers off anyway, it makes sense to replace seals if you don't know their ages.

If you still have the same issue then I'd suspect a microscopic leak at either the master cylinder end or perhaps the banjos at the caliper. New lines (might as well go braided) would be my next move if funds permit.
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Current: 2009 SV650 S, 1990 Kawasaki GT550
Previous: 2009 CBF125, 1998 GSF600, 2004 FZ6 Fazer, 1978 CB400a Hondamatic

[Kickstart]

[NJD]

Went out and gave the calipers a quick clean, nothing overly extensive.

Slider (pictured below) was sticky on one of the calipers so pushed that backwards and forwards and moves alright now.

https://s22.postimg.org/tc6jea9ht/slide.jpg

Beside that perhaps the seal (pictured below) was the only other thing I noticed. Past its best? (all the others look alright).

https://s22.postimg.org/vvqddnpgh/image.jpg

Pads (both look near the same on either side):

https://s9.postimg.org/th1rk0hm7/image.jpg

I'll leave further action for another day given my half asleep antics to do the most basic of jobs today, not my day.

Rolled it down the path backwards, as a basic test, and felt better although is one of those over imagine an issue when something happens or get noticed moments.

Possible test run on another day then whatever, if anything, comes after that depending on how it feels.
____________________
The do it all, T̶h̶e̶ ̶b̶r̶o̶k̶e̶n̶ ̶o̶n̶e̶,̶ ̶T̶h̶e̶ ̶b̶i̶g̶ ̶l̶u̶m̶p̶,̶ ̶C̶h̶o̶n̶g̶ ̶N̶o̶o̶d̶l̶e̶

[smallfrowne]

Did you do the rebuild on the rear? I ask because if you did then I'm wondering why you aren't popping the pistons out and cleaning up the caliper further if you didn't then you're almost at that point now anyway.

By the looks of it the caliper is pretty mucky and some of the muck will have got behind the dust seals (the one that looks wonky/twisted in the picture). I'd pop the pistons out (easier said than done if they're stuck) and clean inside the caliper and the piston surfaces. Then I'd be taking the seals out carefully with a pointy prodding device and cleaning out behind them.

I'm currently doing the same job on a set of 2 pot slider nissins for a Vfr750. A surprising amount of shite and corrosion lurked behind the dust seal that caused excessive friction - reducing the braking force/piston movement to not a lot. Plus the pistons were covered in gunk as well, below the line of the dust seal.

That dust seal on yours might not be quite fucked, but is in need of attention I'd say.
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'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

[NJD]

[NJD]

Righto.

Still deciding if needs to be left alone or is safe to use until I get time to do the rebuild (might try it out tomorrow) but while I ponder that does anyone have any suggestions on what piston removal tool kit would be suitable in the event that a piston gets stuck while attempting to pump them out?

I see plenty on eBay for £30-40 but does anyone have a direct link to one I can trust not to be a plastic useless copy? I'm not willing to spend £70, £90, £100 + that some of them seem to require.

I'd prefer the tool kit over pliers on the grounds when I went to the shop he told me he used on of them toolkits and the longest bit about waiting to get it out was the walk to and from the workshop, so that tells me all I need to know.

Many thanks.

(links on previous thread have shot up in price.. on the toolkit).
____________________
The do it all, T̶h̶e̶ ̶b̶r̶o̶k̶e̶n̶ ̶o̶n̶e̶,̶ ̶T̶h̶e̶ ̶b̶i̶g̶ ̶l̶u̶m̶p̶,̶ ̶C̶h̶o̶n̶g̶ ̶N̶o̶o̶d̶l̶e̶

[ZX-7R]

You wanna try the Tokico 6 pots if you want crap brakes.Look like they could stop a bus,but you would get out braked by a #bikelifer on a stolen moped.
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Current Bike - 2000 ZX-7R

[wr6133]

[kramdra]

Take it to a shop. As much as I hate shops, those are not the questions of someone competent to do brakes. Those need a full strip, clean and new seals. Consider an upgrade to nissin 4 pots if available for your bike.

Ive been given a pair of cailpers, also tociko's, to remove pistons. They are properly fuckkered. I will be connecting up my spare master cylinder to hydruallically pop them out becuase 110psi of air pressure is not going to do it. I did a quick test with air, only 3 out of 8 will move. Connecting this up will take only 5 minutes.

[ZX-7R]

[NJD]

[kramdra]

Use the master cylinder. Preferably while still on the bike. Use a peice of 1/4” bar or a brake pad to keep the pistons even.

Piston pullers are generally rubbish. They will work provided the seals are good and not stuck.

[NJD]

[wr6133]

[NJD]

[kramdra]

res screws will be M4x12 countersunk. They get over tightened which with the countersunk taper will require a lot of torque to undo, more than a JIS/phillips or normal 2.5mm hex socket head will transmit.

www.ebay.co.uk/itm/362012480989
The head wont deform on a 10.9 or 12.9 so it will always come out. Anything else will be single use, including A2-70 stainless.