I don't know how long my XS2 had sat idle when I bought it. I have the front brake off of the fork from when I rebuilt the front end. It seems to me that I should look into the caliper and do a cleanup and new seals. Am I thinking right, or should I just try it "as is" ? Is it pretty straight forward?
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Addressing the front disc brake after years of sitting
- Thread starter tmikeyb
- Start date
If it were me I would take it apart clean it and probably replace the seals.
+2+1
I’d be surprised if it even works , as is. I would go through everything from top to bottom. Master cylinder, hoses, fresh fluid, brake pads, scuff the disc, the whole nine yards.
But that’s me. Your front brake is what stands between you and the front fender of a Buick.
The single most important part of any motorcycle.
It would not have worked at all, as one of you said. Both pistons are seized .Compressed air didn't budge them. I'll soak them overnight and hope that helps a little. But I'm thinking that they're pretty tight. What is the best way to remove them without buying an expensive tool?
The Yamaha brakes are pretty robust, so you may not need to replace any seals or other parts, but you definitely want to take it all apart and clean it up real good. Over time, the groove that the square sectioned o-ring "seal" fits into gets dried brake fluid in it and a crust builds up. Eventually, this forces the "seal" onto the piston more and harder, and the brake starts to stick or drag.
good info, thanks
Use a large C-clamp to compress the pistons back into the caliper a little bit. This will break them free. Then blow them out with compressed air. You'll probably need to "work" them in and out a few times. They most likely won't come all the way out after the first application of the C-clamp.
Personally, I think compressed air is too dangerous to use on badly stuck caliper pistons. I use a grease gun to pump the pistons out. Much safer. But messier.
You're probably going to find the chrome is pitted and the pistons will need replacing along with seals. The good news is that stainless steel pistons are cheap these days.
Worst case; complete new calipers are available relatively cheap.
your master cylinder and brake fluid is the #1 way to move stuck pistons. Helps to do before you remove the brake line, too late for TMB but always worth a mention. But you can hook it back up, bleed and use an MC to pump them out.
5T's "push em in a little" is very good advise. Also lube around them with brake fluid on a q-tip. just did a Honda with stuck pistons, that and air worked for me always cover the piston with a rag. They can easily put a hole through anything nearby. Careful where your fingers are.
Grease guns work as a last resort.... the mess is big.
Often fork oil has doused everything swelling the rubber bits and destroying the pads. Oil soaked pads go straight in the bin, no saving them.
Always; a new brake line.
your master cylinder and brake fluid is the #1 way to move stuck pistons. Helps to do before you remove the brake line, too late for TMB but always worth a mention. But you can hook it back up, bleed and use an MC to pump them out.
5T's "push em in a little" is very good advise. Also lube around them with brake fluid on a q-tip. just did a Honda with stuck pistons, that and air worked for me always cover the piston with a rag. They can easily put a hole through anything nearby. Careful where your fingers are.
Grease guns work as a last resort.... the mess is big.
Often fork oil has doused everything swelling the rubber bits and destroying the pads. Oil soaked pads go straight in the bin, no saving them.
Always; a new brake line.
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Good advice from Gary.
I use a c-clamp to keep the piston from flying out.
Spray rust penetrate on piston, press to bottom and back out c-clamp 2 tuns. Hit with air if piston does not hit piston repeat until it does. when it gets to piston 1 turn in then out 2 turns. If it does not repeat. If it does then repeat 1 in 2 out. Do this until piston is out. A rag over piston is a good idea. I've gotten all my calipers apart this way. Not fast but it works. I have had to soak caliper/piston overnight with rust penetrate. To me grease is too messy.
I use a c-clamp to keep the piston from flying out.
Spray rust penetrate on piston, press to bottom and back out c-clamp 2 tuns. Hit with air if piston does not hit piston repeat until it does. when it gets to piston 1 turn in then out 2 turns. If it does not repeat. If it does then repeat 1 in 2 out. Do this until piston is out. A rag over piston is a good idea. I've gotten all my calipers apart this way. Not fast but it works. I have had to soak caliper/piston overnight with rust penetrate. To me grease is too messy.
OK, I pushed both pistons back with C clamp. Then I reasembled the caliper and connected it to the master cyl. One piston pushed out fairly easily. The other one moved very little, if any. So, I'm a little confused now. Once you've lost pressure because of the removed piston, how do you build pressure behind the other one. I tried expanding an internal bearing puller into the recess of the piston, and was able to move it about 1/16" with a slide hammer. That was the only mechanical means that I could think of to try. I'd rather use air or grease, as you guys have suggested. I just haven't figured out how to seal it up in order to do that. Right now I have it soaking in a little Kroil, and will try something tomorrow.
You have to take the caliper apart as you can see in my pic above. On the outside of the caliper is a threaded hole for the brake line or bleeder depending on which half you are working on. If doing the bleeder side leave it in so it plugs the hole. On the brake line side you can take the bleeder out of the of other side and use it to plug the hole or use a old brake line that has been pinched shut. As far as pressurizing it I use a rubber tipped blow gun to put air in the crossover hole.
Works for me.
Works for me.
Ok, I see. The rubber tip is what I am missing. I'm working with the bleeder side, not the main line side. I just thought that you were somehow making a direct connection from an air hose to the caliper. I don't have a rubber tipped air gun, but I'll find one. So, just so I'll know, how do you connect a grease gun to a caliper?
find a zerk that matches the bleeder valve thread. Hint the caliper can be temp assembled "butterfly" so you have access to both pistons, you can reinstall the loose one and hold it from coming out with a c-clamp so the stuck one can be forced out with the master cylinder..
My Honda brake parts came in, it's off to the bat cave for me.
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I never would have thought about assembling the caliper "butterfly fashion. I'm sure I'll get it out OK using that method. I guess that's why you guys make the big bucks, right?
Another variation on assembling the caliper "butterfly" fashion is to place a small square of aluminum sheet over the crossover hole before bolting the two caliper halves together. This will effectively isolate one half from the other. You can blow either piston out without having to install the other and hold it in place with a C-clamp. Cut a small piece of aluminum out of an empty beer or pop can.
