Bluhdow 16 Posted December 11, 2015 My 2004 DR-Z400S has an issue with the rear brake calipers. Even when the brake lever is released the pads stay pressed against the rotor. Not so much that the wheel is locked up, but enough that the pads will wear over time even without rear brake input. I can see the master brake cylinder is the issue. It's sticking and keeping pressure on the brakes even when they aren't being used. I found this thread which was helpful: http://www.thumpertalk.com/topic/745967-rear-caliper-sticking/ I pulled off my rear wheel and brake pads and then pumped the rear brake to expose as much of the master brake cylinder as possible. I cleaned it up and lubricated the cylinder as well as the pin along which the brake pads travel. Same problem persists. If the thread is to be trusted, it doesn't seem bad enough that I need a full rebuild but I'm not sure what else to try. I see a lot of talk about the rear reservoir bulging but I'm honestly not sure what the means or how to diagnose it. If I did just suck it up and rebuild it I would need something like this, correct? http://www.amazon.com/Master-Cylinder-Rebuild-Dirtbike-OCP-06-651/dp/B00Z81J0LQ Is this a project I could take on myself, or will I run into a hurdle needing some esoteric tool that only a shop would carry? Thank you! Share this post Link to post Share on other sites
Wintyfresh 46 Posted December 11, 2015 It's been a while since I've done one but I think the only 'specialty' tool needed is snap ring pliers. Share this post Link to post Share on other sites
bikeslut 1 Posted December 11, 2015 a recurring issue I have with ONE of my rear brakes... every time I touch the brake caliper area, the pads get off center and drag... So I have to pull them, and reinstall. also... master cylinder vs slave cylinder... I think I'm a little confused. The master is the plastic (usually) reservoir up near the right ankle... the slave is where you pump it to expose the area for cleaning Share this post Link to post Share on other sites
Bluhdow 16 Posted December 11, 2015 Ah, it's the gold cylinder that presses the pads against the rotor. Must be the slave per your description. Apologies for the confusion. Any thoughts or ideas? Thanks! Share this post Link to post Share on other sites
Ken S 164 Posted December 12, 2015 My RMZ 450 has the same issues, let me know when you have an easy fix. Share this post Link to post Share on other sites
Bp619 104 Posted December 12, 2015 Sound like caliper is sticking either a rebuild or new one if can't be rebuilt. There is no slave on a rear brake system just a calipers where rotor is and master cylinder which is connected to your foot pedal. Share this post Link to post Share on other sites
Bluhdow 16 Posted December 13, 2015 I'll pull it back apart today. Clean and reassemble. I'm giving it a 10% probability of it actually correcting the problem. Otherwise I guess I'll just run through brake pads a bit quicker than normal. Are there any other real negatives to a slight pressure on the rotors? The wheel still spins freely, and it brakes just fine, it's just that there is always a light contact on the rear pads/rotor. Share this post Link to post Share on other sites
Bluhdow 16 Posted December 13, 2015 Pulled it apart, cleaned it all up, and same result. I think I'm just going to live with it unless y'all have a compelling reason to rebuild the whole thing (which sounds expensive). In other news, let's go to Lark next weekend! Share this post Link to post Share on other sites
vanjoosten 4 Posted December 13, 2015 Did you clean and re-grease the caliper pins? I have had multiple bikes with weird wear, or brake drag that was caused by seized/sticking caliper pins. A 50/50 grease and anti-seize mixture works well. Share this post Link to post Share on other sites
paulmbowers 236 Posted December 14, 2015 The wheel still spins freely, and it brakes just fine, it's just that there is always a light contact on the rear pads/rotor. 100% normal. Share this post Link to post Share on other sites
Bp619 104 Posted December 14, 2015 As long as its free spinning your good. They will have very slight contact on rotor, Share this post Link to post Share on other sites
Bluhdow 16 Posted December 14, 2015 Beautiful. Thanks guys! Share this post Link to post Share on other sites
