Rear Brake not compressing enough

[slug]

So I got new brake pads in this weekend and I started by changing my back brake. I couldn't fit the new pads in for the old ones as there wasn't enough space between the pistons and disc, so I ended up letting out all the brake fluid, removed the brake caliper, disassembled it and used C-clamps to compress the pistons so i could fit the new brake pads in. I reassembled all of it and added new brake fluid to the system.

To add the fluid I would ensure that the rear reservoir was always full of fluid, I would pump the rear brake a few times and then open the bleeder with an 8mm wrench and close after a few seconds then repeat until the system was full of fluid with no air bubbles. When I fully compressed the rear brake petal (when it touches the exhaust) the pads BARELY rub the disc.

How do i adjust this? I didn't want to mess with the back brake "Pump" without asking as I know nothing about brake systems.

Thanks!

[Janx101]

Bleed it again. .

[DevilDesire]

Hello, last time I did this it took me hell of a lot time... It wasn't on my GS but a scooter tho. I completely removed the fluid and filled the system with air. It took me about an hour of bleeding untill I got it right so I guess you'll have to bleed it to death again and again and again

[Big Rich]

+1

Use a clear hose attached to the bleeder valve, and keep the hose sticking up as vertical as possible. Every time you open it, more fluid / air will come out. With a long enough hose you will get the system bled before fluid spills out the top. Oh yeah - a hose clamp on the bottom of the hose will prevent brake fluid from leaking back onto the caliper.

[DevilDesire]

Oh and something else, sometimes even if 2-3 tries give you no air bubbles there is still air, so you have to continue till the lever stiffens. I tell you this because I had panicked while bleeding that scooter that I had somehow broken the damn thing. 

[gsJack]

Riding my bikes year around here in NE Ohio I get a lot of hard crud built up on the extended part of the pistons that can cause piston binding and brake lock-up if pushed back into the caliper bores and seals so I pop the pistons out and clean them thoroughly every brake pad change with SOS type pads or those green kitchen pads before putting them back in.

When assembling brake hydraulics filling as you go can save a lot of bleeding later.  I fill the bores with brake fluid and then push the pistons all the way in while holding the open bleeder upwards until it's in and closed.  Takes only a few minutes to final bleed the system after it's all together.

If I have one that's full of air like yours I just wrap a rag around the caliper bleed screw area, open the bleeder and holding my finger over the bleeder I can stroke repeatedly to pump air/fluid out without sucking back in on the return stroke.  Be sure to close and fill the master cyl often enough to not run dry.

[slug]

Thanks for the replies. I ended up taking the caliper off again and cleaning the Pistons. They had a lot of build up so I'm guessing that was preventing them from fully compressing. Cleaned and bled again, everything seems to be in order thanks guys!
Glad I didn't mess with the pump

[yamahonkawazuki]

So I got new brake pads in this weekend and I started by changing my back brake. I couldn't fit the new pads in for the old ones as there wasn't enough space between the pistons and disc, so I ended up letting out all the brake fluid, removed the brake caliper, disassembled it and used C-clamps to compress the pistons so i could fit the new brake pads in. I reassembled all of it and added new brake fluid to the system.

To add the fluid I would ensure that the rear reservoir was always full of fluid, I would pump the rear brake a few times and then open the bleeder with an 8mm wrench and close after a few seconds then repeat until the system was full of fluid with no air bubbles. When I fully compressed the rear brake petal (when it touches the exhaust) the pads BARELY rub the disc.

How do i adjust this? I didn't want to mess with the back brake "Pump" without asking as I know nothing about brake systems.

Thanks!

future reference, when you do this again, when you remove the dead pads, take one of them and a c clamp and use it to CAREFULLY compress the piston back in. Eliminates alot of the hassle you are experiencing, been there myself before this trick. Btw if its dot3 fluid, be careful. It and paint are mortal enemies lol