gilbertdave Posted March 3, 2011 Report Share Posted March 3, 2011 Hi all... I've read everything I can on this subject and it sounds like such an easy process... but I just can't do it! My bike is a 2000 Gas Gas TXT 250 with AJP level / master cylinder and Hebo caliper. Being as I'm an idiot I decided to have a look at my brakes and see how they work... First lesson I learned is if you split the caliper, you let loads of air in the system. Ten wally points to me. So, I followed instructions to bleed the brakes and nothing... maybe a little spurt here and there but not the torrent the instructional videos etc online would have me expect... So, I went out a bought a "pressure bleeding kit". I linked the kit up to a tyre at 20 odd psi as it recommended and the poxy thing burst, spraying brake fluid all over me and my shiny red tool box.. triffic. So, I've disconnected the banjo at the caliper... squeeze the brake, nothing... disconnect the banjo at the master cylinder and still nothing. Then I took the piston out of the master cylinder to check for damage or signs of wear and nothing. I am at a complete loss as to how I can't get brake fluid to go through the small hole in the master reservoir and simply spuff onto the floor through the open banjo connection... am I missing something? I've just recently bought the bike and not taken it out for the day yet, but the brakes DID work before I "maintained" them. They dragged a bit, but they were good enough to get the back wheel in the air whilst dicking about on my drive. So... I beleive I've tried everything that the online literature suggests, so now its time to plunder the minds of those who may have had these problems before? Do I A) need to replace a faulty part B.) let someone who knows what they're doing have a look or C) smash everything with a hammer and cry about it? Any and all advice would be gratefully recieved Quote Link to comment Share on other sites More sharing options...
houseape1000 Posted March 4, 2011 Report Share Posted March 4, 2011 Best advice is sit down and have a brew - everything's harder if you're frustrated !!! Have you tried back filling it - remove the res cap, fill a large syringe with brake fluid, connect syring to caliper bleed nipple (open) with piece of snuggly fitted tube (pref clear) and fill slowly until it reaches the required level. I've not tried this myself....never needed to, but believe it works a treat. Andy. Quote Link to comment Share on other sites More sharing options...
spark Posted March 4, 2011 Report Share Posted March 4, 2011 I have quite a bit of unwilling experience in this department. The first thing is to imagine how air will act in your brake system. It only takes a very small bubble to have spongy brakes. If there is a loop in your brake hose before it drops down to the master cylinder an air bubble will want to sit there. A little corner in the caliper higher than the banjo bolt and it may decide to hide there as well pulling faces at your fruitless bleeding attempts. I find the best method is to use a very large syringe, like 60cc. This is connected to the nipple on the caliper with some rubber hose and the fluid is sucked down from the master cylinder. I actually made a larger reservoir from a Motorex brake fluid can that bolted to the top of the master cylinder so I could add lots of brake fluid. If you do not do this you will need to have someone to top up the master cylinder as it drains extremely fast. Sometimes if the brakes are being very stubborn I may reverse bleed as well by filling the syringe with brake fluid and forcing it up into the master cylinder reservoir. Loosening the caliper from the fork and dropping it lower helps get rid of the loop in the brake hose where bubbles like to sit. Lightly tapping the brake hose and caliper also helps dislodge any little bubbles as well. Rotating the caliper so the banjo bolt is the highest point helps as well. I like to end off by turning my bars so the master cylinder is the highest point in the system (caliper still hanging down to get rid of the loop). Then I flick the brake lever in and out whilst tapping the brake hose. Normally any left over small bubbles will come out of the hole in the master cylinder. It may be a good idea to change the seals in the master cylinder whilst you are at it. My bike was less than a year old when my brakes were not as good as when the bike was new. New master cylinder seals brought back the instant hard brakes and got rid of the mushiness. The pistons in my caliper are also coated with what looks like a titanium nitride. I polished the matt surface with diamond paste and a felt bob in a die grinder. Doing this made the pistons slide much easier and got rid of the tick tick noise I would hear from the brake pads touching the floating disc. I can tell you a last resort, but this really is a last resort that I had to use once. I am extremely fussy with my brakes and the one time I just could not get that rock solid feel to the lever no matter how much bleeding I did.It worked fine but it was not perfect. I bought 5 bottles of 500ml brake fluid and filled up an empty 2L ice cream tub. With some latex gloves on I assembled the brake caliper completely submerged in the brake fluid, making sure there was not even the tiniest air bubble, not even behind the seals. Filling up the syringe and reverse bleeding the brake hose whilst having the syringe and caliper submerged guarantees that you cannot introduce any air into the system. This was done on a workbench, not still attached to the bike. Using this method I got brakes that were as good as new if not better. Quite unconventional but it worked damn well. Quote Link to comment Share on other sites More sharing options...
gizza5 Posted March 4, 2011 Report Share Posted March 4, 2011 Yep back bleed it exactly how Andy said it works every time. Quote Link to comment Share on other sites More sharing options...
gilbertdave Posted March 4, 2011 Author Report Share Posted March 4, 2011 Thanks folks...It looks as though I've got a few more things to try. With some luck, I can confirm my success by posting a photo of my graized face as confirmation that the front brake is now sufficiently powerful to pitch me over the bars! Now to find a giant syringe... Quote Link to comment Share on other sites More sharing options...
spark Posted March 4, 2011 Report Share Posted March 4, 2011 I actually got my syringe from the local shop as it was sold as a basting syringe (comes in a packet with a needle and instructions). Alternatively a horse vet cos damn I don't want to think they could use a syringe that size on a human... Quote Link to comment Share on other sites More sharing options...
crasher Posted March 4, 2011 Report Share Posted March 4, 2011 I actually got my syringe from the local shop as it was sold as a basting syringe (comes in a packet with a needle and instructions). Alternatively a horse vet cos damn I don't want to think they could use a syringe that size on a human... make sure your bleed nipple is clear before you start otherwise the syringe pipe will shoot off spraying you again in brake fluid, the nipple is supposed to have a rubber cover but they are usually missing allowing the nipple to fill with mud, another thing you can do is take the circlip off at the plunger on the lever and let the plunger come out a bit as you sometimes get a tiny bit of air in there,then when you have finished push it back in and put the circlip back on, front brakes are actually quite easy but whatever you do don't mess with the rear as they are a pain in the ar5e ! Quote Link to comment Share on other sites More sharing options...
splatshop Posted March 4, 2011 Report Share Posted March 4, 2011 Just a couple more tips that might help: Try pumping the calliper pistons out most of the way then undo the bleed nipple and push the piston all the way back in, this helps remove any air from behind the piston and helps to renew the oil stuck behind the pistons. Some times it is better to suck the oil through, take the bleed nipple off and put some PTFE tape on the threads and replace the nipple so you get a good seal, then using a syringe and a tight fitting tube suck the fluid through the bleed nipple, this can work better as sucking the air causes it to expand making it easier to displace. Quote Link to comment Share on other sites More sharing options...
2shock Posted March 4, 2011 Report Share Posted March 4, 2011 This won't help, but did almost the same thing while trying to 'clean' the rear brake. I tried all the usual methods (and a few unusual ones!) of bleeding it, but before i'd ground my teeth away in anger and frustration called my local friendly dealer who laughed and said ''we get about two a week to do as they're swines - bring it in'' So unless you're the determined type who has to beat these thing's, and actually enjoy's wasting hours in a freezing garage covered in brake fluid, i'd go for option B. It was the best 20 quid i've spent in a while! Quote Link to comment Share on other sites More sharing options...
gilbertdave Posted March 4, 2011 Author Report Share Posted March 4, 2011 (edited) This won't help, but did almost the same thing while trying to 'clean' the rear brake. I tried all the usual methods (and a few unusual ones!) of bleeding it, but before i'd ground my teeth away in anger and frustration called my local friendly dealer who laughed and said ''we get about two a week to do as they're swines - bring it in'' So unless you're the determined type who has to beat these thing's, and actually enjoy's wasting hours in a freezing garage covered in brake fluid, i'd go for option B. It was the best 20 quid i've spent in a while! I this evenings efforts are not succesful, I should imagine I'll find it fairly easy to swallow my pride and have someone else do it. Edited March 4, 2011 by gilbertdave Quote Link to comment Share on other sites More sharing options...
perce Posted March 4, 2011 Report Share Posted March 4, 2011 http://www.youtube.com/watch?v=FcQq4U5ALyk 1 Quote Link to comment Share on other sites More sharing options...
yamxj Posted March 5, 2011 Report Share Posted March 5, 2011 i agree with crasher dont touch the rear i have been at mine a week tried all the methods mentioned except the submerged one could be plan B good luck Quote Link to comment Share on other sites More sharing options...
fastducs Posted March 6, 2011 Report Share Posted March 6, 2011 Regarding the rear caliper - you might find it helpful to remove the caliper from swingarm and elevate it as high as possible. Put an old brake rotor between the pads, and bleed from M/C side. When I fill an empty master cylinder, I find that a hypodermic needle is very helpful. It is small enough to fit through those tiny holes in M/C reservoir to inject brake fluid directly into the M/C piston chamber. Likewise, if the caliper is empty, I completely remove the bleeder nipple on the caliper, and use the needle to fill it with brake fluid. Then I push the brake pads apart to displace the air from the caliper. This won't get all the air out, but it will get the system primed enough to start bleeding it. And don't forget to fill the brake line too. Quote Link to comment Share on other sites More sharing options...
yamxj Posted March 6, 2011 Report Share Posted March 6, 2011 (edited) i have been at it today pushing fluid in through master cylinder it is gradually coming there is a bit of pressure on the peddle ran out of brake fluid another session tomorrow should sort it Edited March 6, 2011 by yamxj Quote Link to comment Share on other sites More sharing options...
spark Posted March 7, 2011 Report Share Posted March 7, 2011 I have completely bled my rear brakes 3 times already for various reasons. I know I should struggle bleeding it from what I have read, but actually every time has gone very easy. I use a combination of sucking and pushing the fluid with the syringe. It is a couple minute job. 1 Quote Link to comment Share on other sites More sharing options...
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