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What did I do to the rear brake.....

Discussion in 'Technical and Troubleshooting Torque' started by deXtrous, Jul 14, 2011.

  1. So, the rear brake on my girlfriends bike was getting a bit stuck and wouldn't retract all the way at the drum. I took the bracket that connects to the drum off. The part is circled here,


    So I took it off, gave it a clean in some WD40 and put it back on. I didn't mark any positions of where the adjustor bolts went stupidly. Read my manual and it doesn't say anywhere to do it, probably because it's common sense.

    So after a bathe in the lube, everything went back on correctly. Usually when the brake pedal is depressed it tenses a cable which pulls that bracket forwards, applying the drum brake.

    The problem now is, when the bracket is moved FORWARD by the cable (pedal depressed) it does not engage the brakes. I tried using my hand to pull the bracket all the way forward, and it still would not engage. Oddly enough when I pull it BACKWARDS (the opposite way the cable is pulled when brake is depressed), the brake engages.

    What the hell did I do? I'll take some real pics in daylight for a better look. The brakes are still within the 'brake lining wear limit'.

    Cheers folks.

  2. Sounds like something is on backwards! Try flipping the arm on the linkage any way it'll go.
  3. I have a suspicion that there's a 'cleat' for want of a better word, which positions the brake backing plate. If you haven't aligned that, the cable has no fixed point to pull against

    but I have been wrong with two-picture internet analysis before :LOL:
  4. Well it's three pictures now so, cmon! :grin:

    Well, to set aside any doubt I had that I put the bracket on wrong, I manually used my hand to twist the 'thing' the bracket connects to either way,


    and it would only engage brake when going backwards... But I guess I'll try and mount the thing any other way I can to see what happens.
  5. #5 bikeboy, Jul 14, 2011
    Last edited by a moderator: Oct 24, 2015
    Well, I'll have a go ;)

    The lever the cable attaches to operates a cam inside the drum that expands the two shoes. It will work if you shift the lever either backwards or forwards. The cable pulls it forwards. My guess is it isn't adjusted properly, and is out of the range of movement using the foot pedal. It needs to be just off the point of engagement before you push the pedal.

    What model bike is it?
  6. It's an 83.

    I have both extended the bracket all the way forwards and all the way backwards, the wheel sticks much more (but still not a LOT) going the wrong way, when it operates normally (bottom of bracket going forwards) it brakes to less an extent.

    Should I service the brakes maybe? ARGH! They were somewhat working before though.

  7. Maybe something as important as brakes needs to be looked at by a mechanic? Would hate to see the rear lock up or fail at a critical moment just to save a few bucks???
  8. We just bought the bike and it's not being used at the moment. Why would I not try and fix it myself? The gn250's are so easy to work on, I'm just an idiot.
  9. I read this some hours ago and have been pondering a response.

    I think there has been an error in reassembly. I don't know whether it's a big error (hard to make - easy to spot - how could he do that?) or a small error (easy to make - hard to spot - I can see why that happened) but I would suggest you pull it apart again and find a workshop manual or an extract from one, or get a local netrider member to have a look at it, or possibly ride it very carefully to a bike shop and get them to look. Or, take the wheel out and transport yourself and the wheel to a shop, ask them to reassemble the rear drum the right way, and then you put it back on the bike.
  10. I'd say you've slipped it onto the spline to far forward. The reason it is working backwards is there is a cam inside the drum and because it's just a cylinder with a flat it that pushes against the two shoes, works backwards too.
  11. I'm thinking that too. Is that gear pic you posted the spline the lever attaches too? If so, do the punch marks still align with the lever now? (And why are there 2??)

  12. There will be a mark on the shaft (usually a small dot) & a mark on the mating part, these need to be lined up. You haven't done this & it is 'out of range' so to speak.

    There is a flat shaft that sits between the brake shoes, moving this either way will engage the brake.

    Hope that helps.
  13. Ding ding ding! AH bit of a light bulb moment after reading that. Went back and readjusted the bracket on the spline and the brake works again, but still sticks :mad:

    Might need a new spring.

  14. The spring inside the drum is critical. Drum brakes are designed to be self activating once the shoe comes in contact with the drum. The spring keeps the shoe off the drum.
  15. I menat the spring on the rod connected to the brake lever, it's used to spring back the bracket into the disengaged position. I just extended the spring with a small metal tube from a pen which gave it more 'spring' (or force) that it had lost somehow.

    Cheers all.
  16. A picture, because I said I would, the back thing in the left of the circle is the metal cylinder, on the right of that is the spring.

  17. :rofl:
    Hammer, boxcutter, WD-40: 3 essential tools when performing brake maintenance...

    Make sure you give that tyre a good soapy wash before it hits the road too.
  18. It's a drum brake mate!! But cheers I will wash the tyre.

    box cutter - scrape rust off exhaust
    WD-40- Clean bracket and stuff to stop it sticking (I did remove them before spraying them, admittedly I did a bit after I put them back on too)
    Hammer - tonk the bracket back in snugly
    ARC welding stick - You missed that one huh!! - Tried to weld a new divot onto the brake rod to compress spring more.
    White stuff - AUTOSOL!!
  19. That spring you're worrying about just keeps a bit of tension between the 'cable' and the brake lever (what you are calling the bracket) and stops the adjuster turning.
    The spring that returns the brake is inside the drum.
    The effect you are getting can be caused by ecxcessively worn brake shoes, but if you have a wear limit indicator and its in limits then that's not your problem.
    I suggest you remove the wheel and brake backing plate, take off the shoes and then you can pull out the splined shaft. Clean up the bearing surfaces and re-install it with a small amount of high temp grease.
    Its very straightforward if you are mechanically inclined................. And dextrous. :)