Scary moment with my brakes

[shielsy]

I took the Hayabusa out for a spin at the weekend and had a bit of a brown trouser moment. On a fairly spirited ride from roundabout to roundabout in deepest, darkest Milton Keynes the bike felt like it lost power quite suddenly. I backed off and opened it up again to find it was really struggling. As i attempted to coast into a layby up ahead the bike came to a rather sudden stop.... By sudden stop i mean it was like a grabbed a handful of brake.

The front brake was seized good and proper, stunk of burning and white hot. Turned the bike off wondering how the fuck I'm going to get it home, so had a smoke. After I'd regained my composure i went to take the bike off the stand only to find it rolled free as a bird. However the brake fluid was clearly still cooking as the lever could be pulled back to the bar with no brake force applied. Waited another 10 minutes and was able to limp it home. Brakes functioned fine during the cautious ride back.

This evening I've taken the (shitty 6 pot) calipers off and gave the pistons a good clean. They were pretty dirty and one or two were a bit sticky... None were what you would call seized though. I rebuilt them this time last year. I flushed through some fresh brake fluid and also gave the lines a good inspection; no kinks or damage found.

I now find myself wondering if there is anything else I need to check. I really, really don't want the front locking up next time. Kind of feel like i may not have found the root cause if you know what I mean.

[jaffa90]

Are you touching the brake lever when riding? Also check freeplay with lever and piston. I would be looking at the master cyl and piston.

[Robby]

Two places I would look:
1. Pad pins. Do they have notches worn in them?
2. Master cylinder return hole is clogged. Usually a fluid change sorts it, sometimes it needs a pin wiggled in the hole to break up any sludge.

[BTTD]

if it was hot enough to boil the fluid, is the disc now toast?

[tom_e]

Cheap aftermarket levers fitted? They could be applying a tiny bit of force even when not in use due to the tolerances being a bit crap and it gradually boils your brake fluid.

[RhynoCZ]

I had simillar issues with my ZX7R. Some pots were just sticking out, so I took the calipers apart, cleaned and rebuilt them. After about 200km something, that nearly put me off riding, happend. I was in front of a corner, just gently applied the front brake, like I always did, and not much happened. So I got into the corner quite fast and the moment I was leaning the motorcycle left, to make the corner the front brake started dragging. Very scary stuff. I had to pull over, had a few minutes to calm down, then I slowly rode it home, stopping 5 times during the ride home checking the front brake was not boiling. Got to my garage, went online and bought Nissin 4 pots.

I know this is the least popular answer, but swap the crap Tokico 6 pots for Nissin 4 pots (Nissin 6 pots if you can obtain a pair). Your issue might be elsewhere though, so investigate before you invest. My fluid never boiled though.

After I changed the calipers for Nissin 4 pots, I never had issues with the front brake ever again. I think it's got something to do with the diameter of the pots. The 6 pot calipers having smaller pots more prone to dirt related issues.

TEST: Take one caliper off, take the pads out, squeeze the front brake lever and then let go. During that watch all the pots in the caliper to go out and then return back. If they don't return, there's you problem.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Polarbear]

Yes, I agree Tokico six pots aren't the best brake in the world (total understatement ) but I never had that sort of issue with the ones on my busa.

I used to giver them an overhaul once a year and they were fine.

I do agree that changing them for Nissins is the easy if not cheap way to go.
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Triumph Trophy Launch Edition

[RhynoCZ]

[shielsy]

Thanks for the suggestions.

Via the process of elimination i was also thinking about stripping the MC, but one thing (which i didn't make clear in my post) was that i believe it was only the RH caliper which was affected. Probably good practice just to do it anyway.

The pins were replaced last year and still look good after a clean and some copper grease. The discs were looking pretty sorry for themselves to begin with so best i sort them out as well.

[Stalk]

With Milton Keynes being roundabout city, did you just cook the brakes? Just thought this may be worth a mention.

[shielsy]

It's been on a few spins to work now and the problem seems to be rearing its head again. I can hear the pads dragging when riding slow and when i try and spin the wheel with the bike in the air, there is some resistance. I can push the bike around fairly easily so it's not terminal.also after 10 mins riding i can touch the disc without getting burnt.

I guess another tear down of the calipers may be in order to check the seals are ok... Not really looking forward to it as i only did it last summer.

[ZX-7R]