Brakes Not Bleeding Help.

Discussion in 'General Scooter Discussion' started by gamecelt, Jul 30, 2019.

  1. gamecelt

    gamecelt Member

    Messages:
    52
    Direct Bikes 125cc Scorpion. Front brakes weren't working so took caliper off and all looks okay. Decided to bleed the brakes. 1. Attached a pipe to the bleed valve. Depressed the front brake and nothing came out of the pipe ie. No brake fluid came through.
    2. Undid the hose connection from the caliper and some brake fluid drained from it. The brake Lever went stiff so I thought to fill the fluid reservoir. Attached the hose connection.
    3. Undid the fluid reservoir that holds the brake fluid and there was none in. So filled it up and depressed the brake Lever. It was slack again and the fluid was not being pumped through the bleed valve.
    4. So undid the hose connection from the caliper again thinking if I depressed the brake Lever it would at least drain through the hose. Nothing.

    So now the reservoir is half full (see pictures) all is connected up ie the pipe on the bleed valve (see picture) but when I try to bleed the brakes by depressing the brake Lever nothing happens except the brake Lever is still slack and does not harden.

    Any help would be appreciated.
     

    Attached Files:

  2. Ian Robinson

    Ian Robinson Member

    Messages:
    41
    Bleeding brakes can be a right sod, at all times make sure that the resavour is topped up, disconect the hose from the brake caliper, unbolt the brake caliper, hold the hose above the brake lever and pour brake fluid into it,you might need to loosen the hose at the lever end, the closer to full the better, in my toolkit i have a syringe that does this well, fill the brake caliper with fluid, bolt it back together without spilling, keep caliper above the resavour, (bubbles rise) bleed it, bolt caliper up without taking it apart if you can but if you have to, try holding a rag over the hose, pouring fluid in is the trick
     
    Last edited: Jul 30, 2019
  3. gamecelt

    gamecelt Member

    Messages:
    52
    When you say 'Pour breaks fluid into it...' do you mean I to the hose when it's above the reservoir? (ie using a syringe to force the fluid in and the air out?).

    When you say fill the caliper with fluid how do I do that I thought it was just the reservoir and hose?

    Thanks in advance.
     
  4. Ian Robinson

    Ian Robinson Member

    Messages:
    41
    Yes try to get fluid into the hose while it is detached from the caliper, and pull the hose off the forks and get it above the brake resavour, back filling the hose helps it to get started, dont forget you might need to loose the hose at the lever end a half turn, a bottle with a pointed top would work, (cleaned out 3 in1 oil bottle) with the caliper i mean just pour fluid into the hole that the hose connects to, every cc counts, then when you put it back together do it fast so as little as pos spils out, the idea off having the caliper above the resavour is that the trapped air rises, pushing bubbles downhill is a thankless task, when its down low the air bubble rise up to the resavour and the piston wont start pumpin, once its up high the fluid runs back to the piston and you canstart to bleed, there is no' one way ' valve at the resavour, so if the hose is empty when you pull the lever 10cc of brake fluid is pushed into the hose, and when you let go of the lever 10cc is sucked back out, geting fluid up to the lever stops this happening, when fluid is up there pulling the lever pumps 10cc into the hose, and when you let go capilery action holds the fluid so only 5cc can run back, a bit indepth but there fuck all on telly
     
    Last edited: Jul 30, 2019
  5. gamecelt

    gamecelt Member

    Messages:
    52
    OKs I'll try the above tomorrow and let you know.
     
  6. Ian Robinson

    Ian Robinson Member

    Messages:
    41
    If you dont have a pointy dispenser, cut a small hole in a bag, push it over the hose and tape it tight, fill the bag with fluid, lift high, loose the hose bolt the lever end, it will run down
     
  7. gamecelt

    gamecelt Member

    Messages:
    52
    OKs I put the hose in a brake fluid bottle and did the above and it did run down. I squirted fluid into the caliper and filled the reservoir. Attached all ensuring the hose did not empty keeping the hose upright so as not to empty it.

    The Lever is still loose and it didn't work.

    Any ideas?
     
  8. Stevep

    Stevep Well-Known Member

    Messages:
    5,895
    Got a compressor?
    Remove the caliper from the bike and put it on the bench.
    Ramp up the air pressure and blow the pistons out the caliper via the hose connection hole.
    When the pistons are out, remove the fluid and dust seals that are in there, clean in the slots and holes removing any crud that can be seen.
    Clean everything meticulously.
    When all is clean, dip seals in new clean brake fluid and install, dip pistons in new brake fluid and install using a twisting motion as you push them into the holes. Push them all the way back as far as they can go.
    Thats the caliper overhauled eliminating any sticky pistons.

    Part 2

    Remove the master brake cylinder from the bike, remove the brake hose from it as well.
    Clamp it in a vice on the bench, in such a way that you can operate the brake lever fully, not too tight or you can break it.
    Fill the reservoir with fluid and look to see if any is coming out the hose hole, or, worse case scenario, around the brake lever end where it pushes the plunger.
    If no fluid comes out then proceed as follows:
    With the reservior full, depress the brake lever fully; at this stage do not worry if fluid comes out.
    While fully depressed, place finger over the hose hole creating a tight seal and SLOWLY release the brake lever.
    You should see the fluid level drop ever so slightly. This should start to draw the fluid into the plunger chamber.
    Depress the brake lever about 1/4 of the way back again
    Release your finger from the hole and then put it back again, creating a good seal
    Fully depress the lever, slowly, keep it depressed, release your finger briefly (should get some fluid out and it releases the air in the cylinder) then apply pressure again
    Slowly release the brake lever; again you should see the fluid level go down. Keep your finger over the hole

    You should now start to feel pressure in the brake lever at around the halfway point of travel, and you should start to feel the pressure on your finger as well when you operate the lever
    Don't go barmy operating the lever because fluid will spurt out the reservoir all over the place.

    If this works (as it should) then the master cylinder is good
    If it doesn't, then the master cylinder seals are shot (it allows the fluid to pass them)

    Two choices if it fails:
    Try and get a master cylinder repair kit or buy a new master cylinder.
    Personally, I'd go for the latter, it's just as cheap.
     
  9. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    7,321
    It's a fickle job sometimes.
    A lot of brake bleeding comes down to experience. You get to feel where the problem is, a dud nipple, master cylinder leaking through or even just a bubble moving forward and back along the brake line.
    Try cable tying the brake on overnight. As in a cable tie round the lever and bars.
     
  10. gamecelt

    gamecelt Member

    Messages:
    52
    Okay fixed. Believe it or not I hadn't tightened the screw at the bottom! I am thick.
     

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