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Old 08-26-2012, 10:58 PM
clcorbin clcorbin is offline
XStremely XSive
Join Date: Jan 2010
Location: Albuquerque, NM
Posts: 495
Long over due brake maintance


Well, I finally pulled the trigger and did some much needed work on the front brakes of my 79F (the rear will happen next weekend). Lately, I have been noticing a bit of sticktion in certain points of the front brake's travel. It was most noticeable when I was stopping at a "normal" rate, then increased the pressure to slow down faster. The brakes would "hang" just a bit before jumping to the higher braking pressure. It has definitely been getting worse fairly quickly, so I decided it was time to do something about it.

I won't go into the details, as has been covered else where. I will say that I got pretty lucky. The bike has lived it's whole life in the high desert of New Mexico (not much rain, hardly any humidity most of they year, very little road salt, etc.), so the piston and master cylinder bores were in very good condition. The master cylinder only needed a VERY light honing to smooth it out around the region it was hanging (I couldn't see it or feel it with my finger, but the piston did hang there every so slightly). The pistons looked almost new, with only a bit of rust near the dust seal on the left side caliper.

The only thing I did not see mentioned in the other threads on rebuilding the calipers has to do with the floating mount. These calipers have one piston and they "float" on a pin to keep equal pressure from both pads on the rotor. The pins on my were both pretty much stuck. I ended up having to use a hammer and drift pin to push them out of the mount that they should "float" in! Once they were out (one each side), they did not look particularly dirty nor were they corroded at all. Just 33 years of aging had turned the factory grease into something resembling glue.

A good cleaning of both the rubber piece and the aluminum pin, followed with a light lubrication with brake caliper grease had them sliding and floating like new again.

The other thing I did a bit different than many is how I bled the brakes, which is usually a pain with a completely empty system (especially the master cylinder!). I have a Motive pressure bleeder for my other vehicles. It comes with a pair of catch bottle that has a flex line connected to a hard line that goes down to the bottom of the bottle. The result in the line is submerged in brake fluid, so there is no way for air to get sucked back up the line and into the caliper.

Normally, these bottles are used with the pressure bleeder to pressurize the master cylinder and force the fluid through the system. FYI, it works BEAUTIFULLY on every single vehicle I have used it on (seven different models at last count). In this case, I felt the pressure bleeder would be overkill and I was right.

I did connect the bottles, one to each caliper and then crack each bleeder open about 1/4 turn from fully closed. I then filled the caliper with fresh brake fluid and ignored it for about 10 minutes as I put up tools and cleaned things up from the project. When I did get back to it, gravity had started to draw fresh fluid down the master cylinder and that was enough to prime the MC enough to start pumping fluid through the system. There was no pump and hold, no opening and closing of the bleeder screws. Instead, I just slowly pumped the handle through full strokes and refilled the master cylinder when it got low.

You can clearly see the fluid coming out of the calipers through the clear lines on the bottles, so it was very easy to see when all the air was out of the system. At that point, I gave it another four strokes just to make sure everything was flushed before tightening the bleed screws and removing the bleeder bottles.

After that, a couple more squeezes on the brake handle had the pads seated (they didn't move during the flush and bleeding as they bleeder was always open) and the a final top up of the master cylinder had it all wrapped up.

All in all, a pretty fast project (I would guess three hours from start to finish which includes a bit of fumbling about for tools and looking info up in the manual to verify that things work they way I thought they did). I almost can't believe the difference in the brake feel and power. The deterioration of the brakes happens so slowly over such a long period of time that we just can't notice it until it gets UGLY! The return to proper operation happens VERY fast, so the before and after is very much night and day.

I would highly recommend you gents dig in and do a bit of spring cleaning on the brakes if it has been a while (aka: you can't remember the last time you did it...). The results are worth it and the cost isn't that bad.
-- Clint
1979 XS1100F - bought for $500 in 1989
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brake, caliper, master cylinder, rebuild

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