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Project CB 750
(startin' to look good!)


Well...I know it will GO, but will it STOP?


Motorcycle brakes are mucho-important.  I want this thing to stop about as fast as it can (which for a stock braking system, is not that fast).  So, what kind of condition were the old brakes in?

Well, let's just say that I used the front brake when unloading it from the truck, and after that, the front brake just wanted to keep on working, even though I wasn't holding it down!  The piston was stuck, but there did not seem to be signs of any fluid anywhere around the caliper - this is good news.

The problem:  Front Brake Caliper Stuck

The solution:  Disassemble and Rebuild Front Brake Caliper

First, I took a picture of the front brake - I may need this later Well, to get the caliper off of the fork tube, I just started to unscrew things.  When you do the same, do NOT remove the bolts that hold the caliper together (there usually are two).  See the pictures below.  I was careful to take note where things came off so I can put them all back together again.  



Front Brake Caliper - on bike Caliper off the bike.  Shows the 2 extractors 
I broke trying to get the caliper apart.
Another view of the caliper right
 after I finally loosened the bolt
Close-up of the bad bolt that was frozen

I'm not sure if you can tell what I had to do to get one of the bolts loose.  I had to cut away a small part of the caliper (which was done with a Dremel cutoff wheel) to be able to get my super Vise-Grips around the head.  The head of the bolt is supposed to come out with an allen wrench type tool (called a cap-head screw), but needless to say, it didn't!

Another view of the caliper right
 after I finally loosened the bolt
Hooking the caliper back up
to the brake line.

Well, needless to say I couldn't get the piston out of the caliper after I separated the halves.  So, the easiest way to get that thing out, is to hook it back up to the brake line.  I had to put the bleed screw back into the caliper obviously.  I was careful to keep the brake cylinder (on the handlebars) filled with brake fluid - the last thing I wanted was to have air all over the place in the brake lines. The piston came out of the caliper with just a few full "pumps" from the front brake lever.

After everything was off of the bike, I cleaned it all.  There was a bit of buildup around where the piston sits in the caliper, but it all came off rather easily with my fingernail.  I sprayed a considerable amount of brake cleaner in the caliper to help to loosen the grime that had accumulated over the last 10-20 years of sitting.  When I was done cleaning, the inside of the caliper was pretty much spotless.  I carefully inspected the rubber seal on the inside of the piston.  It appeared to be in very good condition (no cracks, no dry rotting, no big dents).  Before I took the piston off of the bike, I did check to see if there was any fluid leaking from the caliper, there was not.  I decided to not replace the seal since it was in such good condition - but if the seal showed any signs of cracking, etc - I would have replaced it.

Making the caliper look a bit better...
I really wanted the caliper to look better than it did before I took it off of the bike.  I was determined to strip it down and repaint it.  The existing paint on the caliper came off with little more than a little elbow grease and a medium steel wool pad.  Here's what the caliper looked like after stripping most of the poor paint off.  I was sure to "sand" down any spots where there were bubbles under the paint to the bare metal.  When I was done, the caliper had a very smooth feel to it.


I then plugged the holes with tightly wadded paper towels (a poor man's plug), and masked off the side you can't see in the picture above (the side that mates up with the other half of the cylinder) with painter's masking tape (the blue stuff).  I then painted the two halves of the caliper with high temperature engine enamel spray paint.  While it isn't necessarily brake fluid proof, it is high-temperature resistant.  I've used the paint before with good success on other motorcycle parts.  Whenever you repaint anything, always use multiple thin coats instead of one thick coat (I used three coats separated by 4 hours drying time for the first two, then overnight for the last coat).  Here's the finished product (click to enlarge):


After allowing the paint to dry for a couple of days, I then recoated the piston seal with new, fresh brake fluid, and applied SILICONE-BASED brake grease to the backs of the new brake pads, as well as the outside edges of the pad backs (not to the pad material itself).  To reinsert the caliper piston, place the caliper on its back and carefully put the piston in the caliper on top of the seal (the hollow part of the piston should face the caliper, and the closed end of the piston should face you).  After lubing the piston seal with clean brake fluid, push down on the piston with an even pressure (use a small 2x4 scrap if it helps).  I then placed the brake pads back in (remember to "pin" the back side of the pad or pads to the caliper - if these pins are broke or missing - replace them!).  Lastly, I assembled the rest of caliper back together the same way it came apart.

Back out to the bike...I cleaned off the brake disc (rotor) with some brake cleaner and then slid the caliper over the disc and carefully realigned it with the holes on the fork tubes.  With the help of a friend, we put the spring back in and threaded the caliper adjustment bolt through the spring.  This procedure may vary for you depending on exactly what model you have, but be sure to either note or take pictures BEFORE you disassemble the caliper so you know how it goes back together. 

Well, everything was back on the bike.  All we had left to do was to bleed, bleed, bleed.


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Last Update: Wednesday, December 14, 2005 11:53 PM