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Thread: Brakes issues. st1300

  1. #41
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    Re: Brakes issues. st1300

    well today i :

    - bleeded the system as the sequence.
    - front master cylinder - spongy as hell.
    - took both caliper top hoses, and put them into
    glass of fluid.
    - pump the master cylinder several time , lots of air bubbles came out..
    - re assenbly whole system and bled system again


    everything appears to as it should be with both pedal and front master cylinder feel the correct firmness

    thiose front hoses sure do trap alot of air

    thanks for all the help guys..

    regards

    tony

  2. #42

    Re: Brakes issues. st1300

    When you bleed both the clutch, and the brake system on the ST's, it helps to turn the handlebars to the side(s), then tap the housing(s) to get air out under the castings. Sometimes you need to crack the banjo fittings on the housings just enough to let them hiss for a second. Also, strap the lever(s) down over night, and place a weight on the foot lever, this will allow any hidden air to slowly vent over night.
    .02

  3. #43
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    Re: Brakes issues. st1300

    Hi Igofar,
    That's a good tip , I will remember that for next time.

    regards


    tony

  4. #44
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    Re: Brakes issues. st1300

    gents,

    I drove about 30 miles down a motorway today, and what happen!

    i felt the bike struggling , so I pulled in the clutch and came to a raging stop!

    checked the back calliper and it was fine,

    front master cylinder was hydraulic locked solid !

    front wheel locked solid this time!

    got out the the trusty 8mm spanner and bleed the left calliper upper bleed nipple.( with one squeeze )


    master cylinder was fine after that , so we're the brakes and I continued on my journey.

    Has anyone experienced this before , and what causes it



    Will ill it happen again ???

  5. #45
    John Heath jfheath's Avatar
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    Re: Brakes issues. st1300

    It has been about a month since I last read this thread. I have to say that I'm getting rather worried about your safety !

    It seems that every time you do something, something else crops up to pose a serious issue.

    So just to recap - please correct me if I have this wrong.

    Its a 2002 ST1100. I haven't spotted whether or not it is ABS, but it is of no consequence at the moment.
    You had rear brake locking problems You had a rear calliper with only one seal in the bore
    You've had 'gel' instead of a piston seal in a bore
    The bike was an insurance write-off after crash damage
    The silver clip in the calliper was missing - or was it the anti-squeal plate fitted to the pad backing plate ?
    You removed and reinstalled various brake hoses
    The circlip in the SMC has popped out (once or twice)
    You have cleaned up the SMC bore with scotchbrite
    You have fitted a service kit to the front master cylinder
    Now after bleeding the front brake locks up

    A few comments about the above. The bike was a crash write-off and the brakes weren't working properly. I'm wondering if those two statements are related. Perhaps the brakes not working was the cause of the crash ?

    The previous owner did not have his brakes serviced properly. We know this from the amount of gunge and corrosion in the system. The 'gel' where the brake piston seal should have been is what happens to the rubber seals - it scrapes out like a thick black paste. I've seen it once on a clutch hydraulic seal, after 29,000 miles on a bike I bought. I've never seen it again during the 200,000 miles I have covered on 4 Pans over the last 17 years. I service my brakes regularly and do a full fluid flush about every year.

    If the silver plate that was missing was the location plate for the tab end of the rear pads, then this was possibly removed as it has a ridge in it. Non standard pads sometimes don't have a slot for the ridge. In which case it was removed deliberately. It needs to be there. You say that you have ordered one.

    We do not know the state of the other brake pistons seals. They have also been sitting in the same unchanged brake fluid for the same amount of time.

    We do know that the SMC is still suspect. The SMC is exposed, and the bike has been in a crash, and it wasn't working. Although the SMC activates the rear brake in the garage, we do not know whether the pistons seals properly against the bore, or whether the piston returns properly to clear the tiny compensation port.

    The front wheel lock up is a worry. The front brake circuit is isolated from all of the complex mechanisms of the rear brake. The master cylinder at the front lever applies pressure to the two outer pistons of each front calliper. (The centre piston is activated by the rear brake pedal). It is a straight forward circuit. So why would it lock solid when it started the ride as running freely ?

    Some possibilities:

    There is too much fluid in the master cylinder reservoir. With heat expansion, there is nowhere for the surplus to go.
    The tiny compensation / relief port in the front lever master cylinder is blocked. This prevents the fluid from escaping as it expands when the front brake gets hot. If it can't escape, the fluid gets hotter and applies pressure to the pistons and the brakes grip tighter.
    You have just put a service kit into the front master cylinder. Perhaps this has been put in incorrectly, resulting in the main seal failing to clear the compensation or relief port. Has the piston been inserted the wrong way round perhaps ? The wide end of the seals should go in first.
    Perhaps the callipers are not able to slide from side to side. When the pads are removed, you should be able to grab hold of a calliper and push it in towards the wheel and pull it back out. The calliper should stay in that position (too much grease on the slider pins may cause air pressure to move it back again - which can cause brakes to get hot.
    Igofar mentioned the spring clips in the roof of the calliper. It is possible to put these in the wrong way round, which allows the narrow part of the spring to fall off the backing plate and to trap the pad in position.
    Similarly, previous attempts to fit pads with the spring the wrong way round will damage the little tabs and prevent the brakes from working properly. Both of these situations can cause brakes to bind, get hot and possibly lock.
    The calliper bracket is bent or broken
    The slider pins are bent
    The front piston seals are shot - there is no 'spring' in them to help release the pads .
    The axle spacers which sit on the axle between the bearing and the fork leg have been installed on the wrong side (one is narrower than the other)
    The silver location plates for the tab end of the pads is the wrong one - one has a ridge, the other doesn't I think the rear has the ridge, the front doesn't. The brake pads are designed to suit this plate. If the front and rear pads or plate have been interchanged, the calliper cannot move as it should.
    The retaining pin is ridged or corroded, preventing the pad from moving sideways.

    Have you fitted new copper / aluminium washers to the banjo bolts that you have removed ?

    Read through Avoiding the Pitfalls - it relates to the back brake, as that is more complex, but much of the information applies to the front as well. Also worth noting is the brake testing procedure that I devised.

    You might also find this link informative - to help inform about where the fluid goes.

    If you want to talk over things so that I can point you to things that you may not have thought about, then send me a PM and I'll send you my email address with a phone number. I'm in the UK. In fact we may well have met at Durham Bikewise sometime.
    Last edited by jfheath; 05-21-2017 at 03:00 AM.

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