rebuilding brake calipers

[garyS-NJ]

My '84 xvz12D was sitting for a while before I bought it and all the calipers have one or two seized pistons. So trying to remove these opposing pistons and having a bear of a time. The manual says to use air to blow out one piston while clamping the other and then to rebuild that side and re-install and then hold the cleaned piston and blow out the other.. Rather than clamp the piston it said to use a "piece of wood" to block it. Well I went on youtube and found nothing on removing opposing pistons so I made a block out of 1/4" right angle aluminum. Going to try it tomorrow but at best I will only be able to do one piston at a time. Seems silly as I'd rather remove both pistons.. Is the trick just to get them both pretty far out by holding the stuck one and using smaller and smaller separating shims (I was using a cement trowel) and then at last moment hitting it with air? I suppose this would get one piston out and then I would need to use my piston inside grabber tool to twist and pry the second piston.... who has done this before?> I think Skydoc is doing it as a service..

 

oh crap. my jpg file attachments are failing to upload.. any recommendations here? files only 3-4000KB

[garyS-NJ]

[garyS-NJ]

[garyS-NJ]

Hey btw, my gf just posted above pics using a website to generate a link for the picture because the forum upload tool wasn't working.. am I missing something? ?

[camos]

The manual says to use air to blow out one piston while clamping the other and then to rebuild that side and re-install and then hold the cleaned piston and blow out the other.. Rather than clamp the piston it said to use a "piece of wood" to block it.

When I had a couple of stuck pistons on one side of a front caliper and getting them out was quite difficult because if you try blocking the one that will move there is no room left for the stuck one to move. I ended up clamping the movable one with a pair of visegrips then used pressure from the brake to force the stuck one out. Cleaned it then slid it back in, blocked that pair with a piece of wood then did the visegrip thing on the other free one. It would have been a lot better if I had removed the caliper before starting this job. It was difficult to get the jaws in far enough to clamp the piston.

 

As an after thought, perhaps a couple of 1/8" flat bars with two clamps would have worked much better to hold the movable pistons and still leave enough room for the stuck ones to get pushed out. Didn't want the pistons to come all the way out, just enough to clean the sides of the pistons. After doing that to all the calipers the brakes worked great.

[camos]

Hey btw, my gf just posted above pics using a website to generate a link for the picture because the forum upload tool wasn't working.. am I missing something? ?

Hard to say what went wrong.

When I want to upload an image I first click on the Insert Image toolbar icon which opens a dialogue box with the choice of selecting the image from your computer to upload or inserting a link to an image already hosted on a web server. The only issue I've had is taking too long to save the post after uploading the image. There is a timeout but it is long enough if you don't go get a coffee or something in the meantime.

[garyS-NJ]

Just tried to upload a pic from my computer again and I get same message "message from webpage: upload of file failed". last night my gf tried it on her mac and also tried it opening venture rider.org with safari.. both times same message.. then she did it with the upload URL tab. Clive can you try to upload a pic from your computer (say maybe a hot ex girlfriend or maybe a big fish or motorcycle??)>

[BlueSky]

the file is too large most likely. Reduce the size and try again.

[camos]

Clive can you try to upload a pic from your computer (say maybe a hot ex girlfriend or maybe a big fish or motorcycle??)>

You trying to get me into trouble?

I think BlueSky probably nailed it. Prior to uploading any files to this site I always re-size the image to 640x480 which makes them small enough to easily upload and are big enough to display the subject well.

[garyS-NJ]

My little tool worked well. First front caliper I just cleaned one piston at a time (with them almost all the way out). The second front caliper one piston popped out so I cleaned both that way and left the seals alone (little scrubby pad clean). Bled both fronts but with new brake pads the front right (hand brake) was still a little soft.

[camos]

My little tool worked well. First front caliper I just cleaned one piston at a time (with them almost all the way out). The second front caliper one piston popped out so I cleaned both that way and left the seals alone (little scrubby pad clean).

That's pretty much how I did it too except none of my pistons popped out.

 

Bled both fronts but with new brake pads the front right (hand brake) was still a little soft.

A little bit of give is normal with OEM brake lines. Really old OEM brake lines will most likely have quite a bit of give due to old age. Of course, there is always the chance all the air was not bled out. It is quite easy to mess up the process with a second or two of inattention. This is the method I use which works very well for me.

[garyS-NJ]

Well I cleaned the rear caliper pistons today and bleeding them I got it bled well but still had no brake pressure so I went back to bleed the front left caliper (still effing linked) & even tho it bled fine with the pedal yesterday, now I'm getting endless air with a hand vacuum pump. It's as if it has an air leak in at the metering valve under the neck. Getting dark now and frustration setting in..... I'd think to deli k I just need one brake lune to go from left front caliper to the handlebar master cylinder (& then the big piston master cylinder). Anyone know the length of that line and the banjo bolt size/type (& a source) as well as a suitable replacement master cylinder? (Ebay...).

[garyS-NJ]

And yes I checked the banjo bolts on the caliper and antidive (& bleeder on antidive) and my hand vac isn't leaking.. (I don't get air with the bleeder snugged

[garyS-NJ]

And pumping the foot brake pedal I'd swear I hear a squishy sound (air leak??) Under the neck (proportioning valve).

[camos]

Well I cleaned the rear caliper pistons today and bleeding them I got it bled well but still had no brake pressure so I went back to bleed the front left caliper (still effing linked) & even tho it bled fine with the pedal yesterday, now I'm getting endless air with a hand vacuum pump. It's as if it has an air leak in at the metering valve under the neck.

The MkII's have an intermediate bleeder valve at the steering head that, I think, the MkI's don't have. Not too sure about that though as I've never seen a MKI. If there is no bleeder at that point then there will be a lot more air to remove and also the potential for getting an air lock in the head area.