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No Front Brakes on CBR250R - Tried bleeding, made it worse!

Discussion in 'Technical and Troubleshooting Torque' started by jayp, Feb 17, 2008.

  1. I have a CBR250R.

    I noticed the front brake was spongy as hell but it worked - it was just not progressive and was 'nothing nothing STOP' when you squeezed it.

    Got tired of this and tried bleeding it.

    Every time I pumped the lever to build up pressure it wouldn't, it would just go straight to the grip.

    It did however move fluid out the bleed nipple when pumped.

    Anyway now theres no feeling in the lever at all and the front brakes no longer work.

    Time for a new master cylinder?
    How much it cost for a good condition second handy or should I rebuild this one.

  2. 1) - How old are the brake lines?

    2) - What is your bleeding technique?

    3) - Are there any leakages from the master cylinder or the calipers? CBR250R - Only one front disc?
  3. yeah ur bike is fcuked time to get a new one,

    now u wont will u
    odds are ur brakes arnt farked either just the operator is clueless
    get some help or go to mechanic
    If u get stuck and your nearby (sutherland drop by well give ya a hand)
  4. have you check for leaking brake fluid from anywhere? what is your bleeding technique? you cant just open up the bleed nipple and start pumping. conect a hose from a bleed nipple into a jar full of brake fluid, then pump. are there bubbles evident? if so then the is air in the system.

    if there is no leakage around the lines, or the caliper, i would say that the master cylinder piston seals need replacing.
  5. who wants to bet that the res in empty?

    when your bleeding you need to add brake fluid as you go
  6. Sounds like you got air in there... you need to bleed it out properly and fill it with new fluid, being careful not to get any air there.

    I'm sure the other nice folks here will tell you how to do it. I'm just too lazy. :p
  7. Re: No Front Brakes on CBR250R - Tried bleeding, made it wor

    Sounds to me like you need to put a kit through the calipers and/or the master cylinder.

    After that it will bleed properly.
  8. Thanks for the vote of confidence guys! (sarcasm)

    Yes I know how to bleed brakes, I've done my family's cars servicing for a few years now.

    No there aren't any fluid leaks in the system. There are bubbles evident, but there should still be some resistance. At the moment there is none. And before that there was barely any.

    Only 1 disc. Brake lines are probably as old as the bike 17 years?

    Too bad I'm not near sutherland, I'm around the Lidcombe area. I kind of don't want to ride around with just a rear brake.

    My technique was exactly the same. Hose from bleed nipple to a jar, slightly submerged in brake fluid. I pumped the lever until there was some resistance before cracking the nut, the only problem is I started off with almost zero resistance.

    I filled the resevoir until it was at the mark. Everything was done by the book.

    The hose leading down from the m/cylinder (top banjo bolt) to the caliper has a little split at the top. I'll replace that.
  9. Bike brakes are more finicky than car brakes for two reason:

    1. There is no power assist. For this reason master piston area is critical. Too large and it will have too much area to produce the power, too small and it won't pump the volume to move the pads the necessary distance. This becomes a problem when the seals in the calipers become sticky. If the volume of the master cylinder is on the smaller side then the caliper pistons will just rock in the bore and wont slide.

    If this is what is causing the lack of lever, then jam something under one of your pads (like a screwdriver), then pump the lever to get the other to slide down the bore. This should then give you enough lever to bleed the system.

    2. The second problem is the height of the master cylinder. Air travels up, so the air bubbles tend to build up in the connection just after the master cylinder. Pump the lever like buggery then crack (just enough to relieve pressure) the banjo. do it up again before letting the lever go.

    In the end a caliper kit look necessary.
  10. Thanks Ibast.

    I think its time to overhaul the brakes. Such an old bike.

    I will try bleeding it with the screw driver. Hopefully I get some feel back into the lever
  11. +1, I've found that the sucking-fluid-through-a-tube trick works well, the first time I ever did a brake bleed on a bike (dry system), it took well over 20 minutes before I actually got anywhere, and a full hour before I had something.... :p

    (got it down to 5 minutes now, thankfully :p)
  12. it took me an hour to bleed the brakes on the storm. Next time i need to do it it'll be one of those bleeder kits from ripco.
  13. Hmm.... try it with the bike tipped right over on its side, get somebody to help you. That can help get bubbles out.
  14. Where the bloody hell did you learn that one, Loz?
  15. crack the fitting at the reservoir then pump it bleed it from there then try get pressure at the calipers. Had the same problem on a fewllow netriders bike.

  16. An old poof showed me.
  17. I am going to have to bill you, mate.
  18. I'll give you 50% of everything I make from it.
  19. If you had been paying strict attention, you would have told the brakeless poster to tilt the bike a lot to the left, to allow the air behind the piston to rise into the res, which is achieved by very little movements of the lever. You just wish you were me.
  20. Tilting the bike over ey..
    But wouldn't the fluid just drop out of the open m/cylinder?
    Further more would you need to put I dunno, blankets or pillows under it?