windlestone Posted February 11, 2004 Report Share Posted February 11, 2004 i'm trying to fit new rear pads. the pistons in the rear caliper will not return far enough to allow new pads in let alone pads and disc. any suggestions guys? Quote Link to comment Share on other sites More sharing options...
brucej Posted February 11, 2004 Report Share Posted February 11, 2004 If you open the bleeder screw the pistons will be much easier to push back in. It still takes a fair amount of pressure, though. I did mine by laying the caliper on its side, with the hose and master cyl. still attached to the bike, on a wooden crate that was about axle height. I used a rubber covered hammer handle to push down on the piston. I then opened the bleeder, pushed down on the piston until I thought it had moved far enough, and quickly closed the bleeder before it could suck air back into the system. Try to push the pistons as straight as possible so they don't get cocked in their bores. Hope this helps! Bruce Quote Link to comment Share on other sites More sharing options...
jtt Posted February 11, 2004 Report Share Posted February 11, 2004 Also check that your adjuster at the Master cylinder is backed off fully. Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted February 11, 2004 Report Share Posted February 11, 2004 Chances are you've added brake fluid over time to make up for the fluid that took up the space behind the piston as the pads wore. Now that extra fluid has to go. I'd take the top off the master and take out a little fluid to make room for what's going to come up, rather than cracking the bleeder and allowing air to enter. You might also consider removing the sealing boot and checking if the piston has a ring of rust/crud that you're about to push through the seal. If so, you can pop out the piston with a few pumps of the pedal and clean it up with some fine emery. Quote Link to comment Share on other sites More sharing options...
kevin j Posted February 12, 2004 Report Share Posted February 12, 2004 I have some tapered plastic wedges that I think were for putting under furniture or something. They slide right down in there, then I twist both directions and it pushes one side of the piston then the other back inward. Sometimes I push on the pad and caliper casting, depending on construction. Charlies good point. pushing crud back into the seals can stick the piston in place so it can't float freely. Quote Link to comment Share on other sites More sharing options...
windlestone Posted February 13, 2004 Author Report Share Posted February 13, 2004 thanks a lot lads. i had a seized piston so had to strip the caliper. now i have two free pistons and no brake pedal! Just seems to be pumping air. i had to leave it tonight but will have to sort it tomorrow. The fluid level is not moving with cap on or off and no fluid is coming through banjo bolt if i disconnect it from caliper. Any ideas would again be appreciated Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted February 13, 2004 Report Share Posted February 13, 2004 Get a big ol' syringe from the horse vet and use it to push/suck fluid instead of pumping the pedal. Stick a piece of rubber hose on with safety wire. Quote Link to comment Share on other sites More sharing options...
windlestone Posted February 13, 2004 Author Report Share Posted February 13, 2004 cheers charlie I may seem a bit thick here but when do you close bleed nipple? or is it a bit of trial and error just keep trying pedal till i get one? Quote Link to comment Share on other sites More sharing options...
jtt Posted February 13, 2004 Report Share Posted February 13, 2004 Just push the fluid through till it flows out clear with no bubbles. Then stop and tighten the bleed screw. After the bleed is tight, you can remove the hose and syringe. Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted February 14, 2004 Report Share Posted February 14, 2004 If you're pumping the pedal, you always open and close the nipple while the pedal is fully depressed. Even after you've done everything right, it'll tale a few pumps to get any pedal because the pistons in the caliper have to come out and contact the disk. When using the syringe, I always keep fluid in it, and as I put the hose on the bleeder (whith the hose just in contact with the bleeder) I pump out a little fluid as I stick the hose on. This way, there is fluid in the hose, so, when you crach the bleeder, if anything gets sucked in, it's fluid...not air. I always close the bleed nipple as I'm working the syringe (working the syringe with one hand and closing the bleeder with the other). I don't know if it reduces chances of sucking air, but I've been doing it that way for years, and it makes me feel better. The trial and error can come in when you're figuring out if it's better to push or pull the fluid. Front brakes respond better to pushing the fluid up from the bleeder. (No point in trying to pull air down and out when it wants to go up). This means you'll have to keep removing fluid from the master or it will overflow. Rear brakes are trickier because air can get trapped in high spots in the hose. I've heard of people hanging bikes by a wheel to get the hose vertical. I prefer to unbolt the caliper and hang IT. Quote Link to comment Share on other sites More sharing options...
windlestone Posted February 14, 2004 Author Report Share Posted February 14, 2004 still no pedal. got a syringe and hose today. syringe is about 4" long and 1" in diameter. the clear hose or tube is an excellent fit on syringe and extremely tight on bleed screw. Pulling syringe plunger out with or without fluid in tube did bring a few spits of fluid and what seemed to be a fair amount of air into tube. as soon as i shut off nipple and started again with syringe it was like being back at square 1. Pushing plunger the other way did not make any impression at all.While all of this was going on my fluid level did not drop??? I did a very basic air test on caliper and air was coming through bleed nipple hole. i removed the exhaust, yes exhaust then removed the master cylinder. did an air test on hoses and they appear clear. Emptied reservoir and feed pipe air tested fine too. Took master cylinder apart and to be honest i'm a bit baffled as to how it works. anyway it has one spring, one central rod with two seals on it and a central groove.The central groove does not appear to line up with inlet or outlet? the rear seal is tapered so the only conclusion i could draw was that the rear seal must collapse under pressure to allow fluid to circulate. Put a high vacuum pump on to bleed nipple and it is drawing fluid and air. i've had enough for today so i'll go back to it tomorrow. thanks again for all the help it,s much needed and appreciated Quote Link to comment Share on other sites More sharing options...
glenn Posted February 14, 2004 Report Share Posted February 14, 2004 Hi gary I did the rear brake on the TXT i had before the pro, it was a right pain in the @rse. I ended up having to take the swinging arm out as sugested by Alan at white Bros. Theres to many bends in the pipe where air can get traped. if you get stuck send me a mail i may be able to come up and lend a hand. i presume you won't be riding tomorow. Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted February 14, 2004 Report Share Posted February 14, 2004 Right....brake hose inside the swingarm... might be time to throw a rope over a tree limb and hoist that bad boy up Maybe removing the swingarm is a better idea. Quote Link to comment Share on other sites More sharing options...
windlestone Posted February 15, 2004 Author Report Share Posted February 15, 2004 hope i can keep the forks in lads they look ok not riding now glen thanks for offer of help. niaevely i assumed pipe inside swinging arm would run straight through. i'll try high vacuum pump then if no good out with swinging arm. i'll leave chain tensioner well alone... heard they are a nightmare. think i'll go back to 348 mont after this Quote Link to comment Share on other sites More sharing options...
windlestone Posted February 15, 2004 Author Report Share Posted February 15, 2004 another day and still no brake at pedal. can't understand logic of swinging arm coming off cos hoses will still need to be connected and caliper. i've had bike upside down and sideways and i'm sick of it now! Quote Link to comment Share on other sites More sharing options...
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