gremlin1988 Posted March 12, 2014 Posted March 12, 2014 Hi I haven't had as much chance to ride my Dragstar Classic recently, and unfortunately found the front brake had siezed when I went to take her out the other day. Taken the caliper off, cleaned the pads and caliper up (fair amount of corrosion / dirt around the caliper as she'd been sitting out uncovered) without any issues. But when I went to replace the pads, I was only able to compress one of the pistons. The other just starts pissing grease / fluid when I squeeze it, and doesn't actually compress. So I think I need to rebuild the caliper, or at least take it apart for a more thorough clean. I've always shy'd away from working on my own brakes in the past, any more than a basic pad clean-up. Can anyone offer any advice, steps take, and caveats to watch out for? Thanks Tom
Noise Posted March 13, 2014 Posted March 13, 2014 Hi Tom, First things first id get onto here http://www.wemoto.com/bikes/yamaha/xvs_650_drag_star/97-04/picture/stainless_steel_piston_and_seals_front_caliper/ and buy the Stainless steel pistons and seals before you go any further. The pistons should "just" pull out, but as you have a problematic one you may benifit from using a bit of WD40 to get it lubed up then get a set of mole grips and turn the piston as you Gently but firmly pull it out. Once both pistons are out, remove old seals and give the whole caliper a good clean with some thing with brake dust remover. Install new seals and Stainless steel pistons and say good bye to seezed pistons for ever.
gremlin1988 Posted March 13, 2014 Author Posted March 13, 2014 Thanks for the advice Noise. Noob question coming up ... Is it necessary / recommended to drain the brake fluid out of the system before removing the old pistons? I know it makes it easier to compress the pistons if you remove some of the fluid from the master cylinder, and assume that in order to remove the pistons and seals I'd have to completely drain the system? Thanks Tom
Campaman Posted March 14, 2014 Posted March 14, 2014 I would completely drain it and put in new fluid, if you have a seized piston its probably rust that's caused it and that contaminates the fluid.
Noise Posted March 14, 2014 Posted March 14, 2014 Yer as campaman said rust must defiantly will be the reason it's seized. Also new fluid will make the brakes work better as you never know how long it's been in there.
gremlin1988 Posted March 14, 2014 Author Posted March 14, 2014 Thanks for the advice Campaman and Noise. New pistons ordered, hopefully back on the road next week.
gremlin1988 Posted April 19, 2014 Author Posted April 19, 2014 FINALLY got round to sorting this out this weekend. Got the caliper off, old pistons and seals out, good clean, new seals and pistons installed, caliper re-installed onto the bike, brake lines connected. But... When I bleed the brake lines there's absolutely no pressure in the system. I can pump the brake lever for 10 minutes, but every time it goes straight back to the throttle grip, no pressure build-up felt at all at the lever. I've removed the caliper from the disc to check that the pistons were extending, but they're not. When I pump the brake lever both pistons extend about 1mm, then retract when the brake lever returns. When bleeding the system new fluid is pumped out of the bleed nipple, so there isn't a major blockage in the line, and some pressure must be present for the fluid to be pumped. But no-where near enough to operate the pistons. I've checked for fluid leaks and can't find any. At this point my assumptions are either an air leak or air blockage in the caliper itself. I'm getting to the point of taking the caliper off and starting again, but before I do, has anyone got any suggestions on what else to check or do? Thanks Tom
Moderator drewpy Posted April 19, 2014 Moderator Posted April 19, 2014 raise the caliper up above the M/C if you can and put something in between the pistons to stop them popping out. some peeps can get a syringe and pump in fluid from the bleed nipple, once you get fluid in the system it becomes easier. I have got a clear tube and sucked the end whilst pumping, that sometimes does the trick. (don't drink it though) another trick is the tape the lever to the bars over night and the air will travel to the M?C but only if you have fluid in the system.
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