Stuck brakes

[jamman18]

Just changed out the front pads on my 1977 750 ss and bled them.  The lever is pretty tight and doesn't travel far. I rode the bike down the block and did not have to apply the front brakes as  they slowed me down on their own.  Is there another adjustment that I missed so that the pads don't continually rub?  I'm frustrated here!

[TOOLS1]

Did you loosen the little screw on the mounting plate that holds it against the fork? It needs to be adjusted, so that the inside pad is about a 1/32 of an inch away from the disc.
If that's OK then you might need to remove, and clean the caliper, but it is easy, and the rubber O-ring is reusable.
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[jamman18]

Thank you.....had no idea that I needed to adjust that.  I will look into that next.

[jamman18]

I actually took a look and do not see any signs of the adjusting screw.  this is a 77 750f ss if that makes a diff......

[TOOLS1]

You just have to be different, don't ya
Your's has the calipers that slide on two bolts, and not swing on a pivot. When they are sticking try loosening the bleeder and check to see if the wheel spins. If the wheel does not spin free try cleaning, and lubricating the bolts it slides on. If it still sticks after that you will need to rebuild the caliper. If loosening the bleeder releases the wheel to spin you will need to rebuild the master cylinder.
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[bundyman142]

my back brake does it to

[TOOLS1]

Welcome to the forum.
Just go through the steps I listed above, for Jammin. Once you figure out the cause. We can talk you through fixing it.
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[Mick]

Can I recommend you buy a vacuum brake bleeder when you do this work, I have spent I dont know how long over the years twisting spanners and pumping levers and holding bottles to bleed brakes. I bought a vacuum bleeder when I replaced the front calipers on my 93 750 Nighthawk a month or so back, from ebay, its a sealey, but lots of folks do them, cost about $50...turned the job from a right pain into an easy one taking a few minutes...Should last alifetime and will work on any bike or car...

[TOOLS1]

I have a Mityvac break bleeder. It also does a pretty good job, and also tests other vacuum operated accessory's on vehicles. another good option is Speed bleeders. they have a built in valve that only lets fluid out, and not let air in. All you do is loosen them quarter turn, and pump until air stops coming out. Then tighten it back down.
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[jamman18]

 "If the wheel does not spin free try cleaning, and lubricating the bolts it slides on."

..meaning the 2 bolts I removed to take the caliper off that have the rubber boots behind them?

If I wind up having to rebuild the Master or the caliper, how expensive and costly is that to do myself?

[TOOLS1]

Yes those are the bolts. The kits for rebuilding the calipers, and the master cylinder are both around $25-$30.
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[jamman18]

It's wierd.....I changed the pads on Monday and rode the bike all over without issue.  I sat for days and when I went to ride it yesterday the fronts were stuck. Seems like if they were going to do that they would have from the beginning.

[jamman18]

Well, I loosened both bleeders and the bike started rolling......so this means the master needs to be rebuilt?  Is there a good video or instructions on the net that you can recommend?

[jamman18]

I took the right caliper off and the bolts are lubed. I checked the rubber pieces with the springs and they seem to push in and spring back fine. The retainer spring for the pads might have been in the wrong way so I put it back in the way that seemed correct and fit a bit better. I need to check the other side and try them again to see if they still stick. That'll have to wait for monday, though as we have Easter activities this weekend. I'll keep you posted.

[TOOLS1]

Here is a good video on rebuilding the master cylinder. http://www.youtube.com/watch?v=2W24asyNujs But I would recommend that when you order your rebuild kit. To also get the long reach C-clip pliers. They are the only thing that will get the second clip out. I bought mine from vintage cb 750 for $10.00.
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[jamman18]

Thanks, with that being said, can you explain physically how the front brakes work as far as what is happening with the master that is preventing it from allowing the front pads to retract?  I'd really like to understand what is happening from applying the lever to when the pads hit the disc.  

[TOOLS1]

I just realized there are two different Jammin's asking questions here
Lets see here. How do hydraulic disc breaks work? When you squeeze the lever. It pushes a small piston past a very small hole in the reservoir closing it off. Now the sealed off fluid only has one way to go. Through the lines to the caliper. Once there it pushes against a larger piston. The larger piston then pushes the break pads against the rotor. The caliper is mounted, so that it can move, and center itself against the rotor. This way it applies equal pressure on both sides of the rotor. When you release the lever. the small piston travels back across the very small hole releasing the pressure. If gunk, or corrosion has built up here it will plug the hole, and not allow the pressure to release. At this same time the piston in the caliper must release pressure on the pad's, and rotor. The caliper must be free to move, and release the rotor. Also the the piston in the caliper must be free to move. The rubber O-ring is supposed to expand out when the piston moves out. Then when the pressure is released it is supposed to pull the piston back a fraction of an inch to release the pads from the rotor. If the piston has corroded, or gunk built up. The piston will not be pulled back that fraction of an inch to release pressure on the pad's, and rotor.
Hope this explains it.
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[jamman18]

great explaination!   thanks!

[jamman18]

So if I understand correctly, by opening the bleed valves and allowing the wheel to turn it tells us that the piston is not sticking and the prob but that would leave the master.  Is there any way to loosen that little master piston up? I noticed in the video that he talks about soaking the master since the fluid is water-soluble.

[TOOLS1]

You could try loosening the line, and removing the break lever. then pushing the piston in, and out with a stick, or something with a flat end that would not harm the rubber dust seal. this might flush out the contaminants. You might have pushed a bunch of gunk back into it when you pushed the piston back into the caliper, for the pads to go on.
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