Hello, I'd be grateful for advice and opinions about why my front brakes locked up. The bike was hot as a result of riding in heavy, slow-moving town traffic when the front brake started binding. I had just time to get to the kerb when the front brake locked up. I let the brake cool and it freed off. I rode home, nervously, using mostly engine braking and the rear brake to slow. The discs are unwarped and the pads are within tolerance. The master cylinder is correctly filled -the fluid is between the level marks. I intended the (highly competent) mechanic to change the brake fluid when I had other work done on the bike recently. I now realise that wires may have got crossed between me and the mechanic about this, so right now I don't know if the brake fluid actually was changed. I'll check this on Monday. And I'll be more careful to avoid the risk of crossed wires in future! I'd be grateful if someone can suggest the cause of the problem.
I think you'll find the adjustment screw in the lever that operates the cylinder plunger (it should have clear visible locking compound from the factory) has been adjusted and is preventing return to the master cylinder. If you do a search you should find the correct procedure for adjusting it back to where it should be, but take care as it's quite likely brake fluid will be squirted out, so cover everything nearby.
Happened to me with a BMW R80/7 once. Luckily for me the brakes were useless. Dread to think of this happening on a bike with really good brakes
Sounds more like one or both the calliper need a strip down, remove any corrosion, build up of dirt etc, make sure all the pistons move and not stuck.put back together with a bit of copper grease.
I hate to put a spanner in the works, you are all right afaiamha, it’s because of the extreme heat in this country that we are not used to resulting in unusual occurrences. My back brake locked on on the multiStrada at the beginning of the really hot weather. Re: 900ss - If any of the eight caliper pistons were just slightly grimy and even thinking about sticking then it only needs the hot weather to hinder retraction enough to start to generate heat leading to heatsoak/fluid expansion which might lock on only when you come to a standstill. Equally the play at the master cylinder might be enough for normal temperatures, but not quite enough for this kind of weather. I think I stated in another thread that one summer I had to add 2 to 3mm to the play in my 748 back brake actuating pin. As also said, a blocked hose can cause the same, as can an over filled master cylinder and blocked breather vent in master cylinder cap - all more likely in hot weather.
Hi everyone, Sorry not to reply sooner. I'm off to see the (highly competent) mechanic, tomorrow, armed with all your good advice. I'll let you know how I get on. BTW when I had a look there was no anti-tamper glue on the adjusting screw....
Hi everyone, Well, the problem has been solved (I think). First of all, the highly competent mechanic ("HCM") had not previously touched the brakes, so the problem was not of his making. When HCM examined the master cylinder he found that the return port was blocked - and also that the brake lever had been adjusted so that the return port was obscured. If I've got it right, either one of these on its own would have caused the problem. Now the return port has been unblocked and the brake cylinder adjusted so that the return port is no longer obscured. The return port is now doing its job, and though the brake lever is nearer the handlebar than before, it feels perfectly OK (and does not come back far enough to touch the handlebar. But...… Firstly, there was no way to create free play between the brake lever and the plunger, however. Related to this, there was nothing but the brake lever to stop the piston emerging from the master cylinder body. Is all this as it should be? Secondly, I'm not sure why the problem did not occur much sooner than it did, given the state of the master cylinder? Was it just that I was riding the bike in far hotter conditions than normal (which I was) and the extra heat was enough to cause drag, fluid expansion and a vicious circle of over-pressurisation? Anyway, it all seems fine now (I think). Thanks everyone for your help - and sorry to keep you waiting for this instalment. Have a great weekend!
It's always nice when someone follows up on things like this, so thanks for the update Have a great weekend too, and hope that the bike rides as intended now
Aw, thanks Desmoquattro, for taking the trouble to confirm this. I've had such a lot of help from the forum, and all the replies to my initial post on this thread are another example of that. Thanks, everyone!
Just reading this thread as I’ve had the same problem on my 750SS. Sadly, my ‘mechanic’ changed the brake discs, pads and brake lines before realising! Quick question...where is the port release hole thing?!?
