Disassembling the calipers and master cylinder

From the outside my calipers looked "OK". My GPz550 only has about 15,000 California miles on it, so stuff generally looks good. But it's 31 years old so this needs closer inspection. When I test rode the bike before riding it, the seller said the brakes had been freshly bled, and they did have pressure. But on my short and slow test ride the pressure varied a lot, and once the lever came back to the bar! Not cool. I haven't ridden the bike since. ;-)

I loosened all the bolts before I pulled the entire front brake system from the bike (as all those banjo bolts and caliper split bolts are hard to loosen when you are holding the caliper in your hand!). To remove the piston from the first caliper I was able to use pressure from pulling the hand lever. But to get the piston from the other caliper I've heard people use air pressure. Hmm... thus I ended up cutting one of the lines and making this gizmo: 

When I pulled the dust seals, I found one was actually torn. And here is how the piston bores looked. On the left you can see some corrosion just inside of the oil seal and on the right ( the other caliper) you can see a line of build up that must have been "behind" the piston.  

Opening the master cylinder things looked pretty gunky.

And it looked gross down the bore as well.

 The good news is all of this looks to me like it will polish right up up. So here are all the parts ready for cleaning: