Over the past few days I managed to get the front master cylinder and both front brake calipers cleaned up and rebuilt.
They were all a complete mess.
On the master cylinder the brake fluid reservoir was full of mud and leaking at the base, the piston was frozen in the barrel and the whole thing was covered in brake fluid.
I tore it apart and cleaned it up. I did some searching on the internet and discovered that denatured alcohol is a good brake fluid solvent. So I used a lot of rags and Q-tips to clean out all the nooks and crannies.
The bore was caked with hardened brake fluid and aluminum corrosion, and I ended both scraping it out with wooden popsicle sticks dipped in alcohol (worked great) and honing it with some 1500 grit sandpaper and my drill (again lubricated with alcohol.)
Once I was satisfied with the state of the bore and had all the parts as clean as I could get them I installed the new piston assembly and put it all back together.
Doesn’t that look nice?
Then I moved on to the front brake calipers.
Removing the pistons was actually kind of fun. I’d heard you could blow them out with compressed air, but I had never tried it.
Sure enough, I put a rubber nozzle on my air hose, pressed it against the inlet and let her rip. POP! Out came the piston.
Make sure you have rags covering the caliper – the piston will come flying out, and so will the brake fluid.
One of the cylinders was full of sludge.
On the plus side, the bores and pistons all looked great after I cleaned them up! I dunked the caliper halves in my gallon of parts cleaner and they cleaned up pretty well. The pistons I just wiped clean with alcohol.
New seals, bolts and an o-ring and we are back in business!
Here is a before and after comparison.
Now I need to get some new braided brake lines and some pads and I can put the front brakes all back together!
One step closer to getting the bike back on the road.