jimster Posted June 22, 2018 Share Posted June 22, 2018 I removed the rear wheel on my 2015 FJ-09 in order to have a new tire installed. After re-mounting the wheel I needed to slightly compress the caliper piston in order to get the caliper onto the brake disc. I then buttoned up the wheel etc. However the brake doesn't want to "pump" back up to the former position and requires a lot of pressure to stop the rear wheel. And then the piston won't release the caliper. I have to pry it away from the disc before it'll release the wheel and allow it to spin again. The wheel will then turn freely again until I try to pump up the brake. Hopefully someone here has had this situation and found a remedy. Thanks a million. JimSTer Link to comment Share on other sites More sharing options...
BentAero Posted June 22, 2018 Share Posted June 22, 2018 I had the exact experience you describe a few years ago on a Honda. It was actually the master cylinder sticking, not the caliper. The master cylinder piston would push fluid down the line applying the caliper piston, but the MC piston was sticking in the 'on' position, which blocks the relief hole that allows the fluid to return to the MC once released. MC needed a rebuild kit, problem solved. YMMV. Keep Asheville weird! Link to comment Share on other sites More sharing options...
jimster Posted June 22, 2018 Author Share Posted June 22, 2018 Thanks so much for the info. I had the same thing happen on an older Honda. However this is a 2015 FJ-09. Do you think thats possible on something this new? Link to comment Share on other sites More sharing options...
BBB Posted June 22, 2018 Share Posted June 22, 2018 Easy to check: remove the caliper, take out the pads and put a thin bit of wood in there so the pistons can’t push out fully. Press the back brake gently and watch the pistons move. Check that they are clean whilst you’re there and then see if they are easy to push back in. This will help to rule out the MC as if the pistons don’t move in easily then it must be the pistons themselves at fault. Red 2015 Tracer, UK spec (well, it was until I started messing with it...) Link to comment Share on other sites More sharing options...
jimster Posted June 22, 2018 Author Share Posted June 22, 2018 Thanks for the info BBB. I checked this and everything moves smoothly and looks clean. I noticed that rear brake reservoir appeared to be over fun and I took some of the fluid out. This changed nothing. I replaced the fluid as it was cloudy looking. Now I have the ABS, check engine and TCS lights on when I turn on the ignition. The TCS goes out but the other two stay on. I know the ABS light is suppose to go out after you start to move. I took the bike out into the back yard but the ABS and check engine light stayed on. HELP Link to comment Share on other sites More sharing options...
duhs10 Posted June 22, 2018 Share Posted June 22, 2018 @Jimster make sure both ABS/wheel speed sensors are seated fully into their mounts.. as easy as they are to install it is also easy to have them slightly off as well. '15 FJ-09 w/ lots of extras... Fayetteville, GA, USA Link to comment Share on other sites More sharing options...
jimster Posted June 22, 2018 Author Share Posted June 22, 2018 Both ABS sensors are snug in their proper place. Link to comment Share on other sites More sharing options...
norcal616 Posted June 23, 2018 Share Posted June 23, 2018 since you have a 2015 you can use the diagnostic feature via the dashboard... you just may need to clear any faults or check to see if the wheel speed sensors are working... 2012 wr250f - C-class 30+ age group 2015 fz-07- Hordpower Edition-80whp 2015 fj-09- Graves Exhaust w/Woolich tune by 2WDW @120whp Link to comment Share on other sites More sharing options...
BentAero Posted June 23, 2018 Share Posted June 23, 2018 Easy to check: remove the caliper, take out the pads and put a thin bit of wood in there so the pistons can’t push out fully. Press the back brake gently and watch the pistons move. Check that they are clean whilst you’re there and then see if they are easy to push back in. This will help to rule out the MC as if the pistons don’t move in easily then it must be the pistons themselves at fault. Not true. *If* the master cylinder one-way valve is sticking, (which would block the bleed hole that allows fluid to return to the master cyl reservoir) the caliper pistons will still squeeze the rotor/wood, but won't release, as the fluid can't travel back up the line. The pedal will still move/feel normal. If the caliper pistons are stuck in the 'squeezed' position, try tapping on the master cylinder with a hammer handle. If the mc piston pops loose, it will relieve the pressure from the caliper pistons allowing the rear wheel to rotate. You've got nothing to lose... Keep Asheville weird! Link to comment Share on other sites More sharing options...
jimster Posted June 23, 2018 Author Share Posted June 23, 2018 Thanks a million for your input, BentAero. However I tried your idea but was unable to get the wheel cylinder to release. Darn it! Link to comment Share on other sites More sharing options...
jimster Posted June 25, 2018 Author Share Posted June 25, 2018 Thanks for all the help guys. Took the rear wheel etc all part again yesterday. I wanted to make sure that all the important parts were properly lubed. While I had the wheel out I re-installed the caliper on the bike. I fond a piece of aluminum that was exactly the same thickness as the rotor. I put it between the brake pads and pushed the brake pedal until it closed on the aluminum piece. I let up on the brake pedal and the piston released the aluminum part. I tried this several times and it worked properly every time. I reinstalled the rear wheel and all the there parts. I double checked the chain adjustment bolts to make sure the wheel was square in place with the swing arm. I spun the wheel and stopped the wheel by applying the rear brake. The brake pad did not release like it should. I took it for a short ride and the disc heated up as before. This has been a tough one with no end in site. Link to comment Share on other sites More sharing options...
BBB Posted June 25, 2018 Share Posted June 25, 2018 So, the caliper pistons and MC work as they should, when the caliper is off the rotor. But as soon as you put the caliper back onto the rotor it sticks again? Could the rotor be warped? Are the caliper pins clean and greased? Red 2015 Tracer, UK spec (well, it was until I started messing with it...) Link to comment Share on other sites More sharing options...
Supporting Member betoney Posted June 25, 2018 Supporting Member Share Posted June 25, 2018 Are the caliper pins clean and greased? I was going to suggest the same thing. From your description, it sounds like the caliper is working fine, until you install it back on the bike. This video ---> might offer some maintenance tips to go over the rear caliper from every angle. ***2015 Candy Red FJ-09*** Link to comment Share on other sites More sharing options...
jimster Posted June 25, 2018 Author Share Posted June 25, 2018 I suppose the rotor could be warped. The bike has less than 6K on it. Whats more likely is the dealer who mounted the tire bent the disk while mounting the new tire. Although I have spun the wheel by hand and watched the rotor spinning between the pads. I can't see any deviation while it's turning. I guess we need to get a precise machine tool to check that. And yes, I cleaned and greased the caliper pins. Link to comment Share on other sites More sharing options...
jimster Posted June 26, 2018 Author Share Posted June 26, 2018 My Yamaha dealer kindly worked me into his schedule this morning and found the problem. I apparently installed the shoes incorrectly and while torquing everything down, I bent the inside shoe. However it seems to be working fine and I'm suppose to let them know if I want them to order a set of shoes that they didn't have in stock. Well, live and learn. And thanks to everyone who chimed in here to help out. Link to comment Share on other sites More sharing options...
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