It's easier to do the calipers when they arecworking than once they exihibit problems ..
Taking apart parts that move is way easier than once they get stuck..and you will likely find they work better when you are finished...
What he said Rob.
And as posted above gunk likes to settle in the low places.
The gunk has acidic qualities due to make up of brake fluid and moisture retention.
If you are replacing the lines anyways might as well clean the calipers also.
Fairly easy job and you know everything is good when done.
The most difficult part is taking out the pistons.
You pump them out.
On Basecliffs site there is a tutorial.
Brake Caliper Overhaul
(by Mr. Stefnwolf)
Be sure to pay attention to the use of the spacer in above tutorial.
The first time I rebuilt breaks I was not aware of this or Basecliffs site.
Without the tutorial and the use of a spacer as described within the piston removal for the one that did not want to budge was a real PITA.
Remember to clean everything well inside and out.
There are a couple of (socks?) not sure on the correct term that slide over the holding pins.
I ripped one by being careless so pay attention when putting back together.
Clean the pins good of baked on crud and insure the travel for the pins is smooth and then grease as per manual.
I used regular grease but a high temp would have been ideal.
There is also a bleeding tutorial on Basecliffs site.
I made my own version of a mighty vac though instead.
Heavy rubberized foam
A deep wide mouth tin can.
Fuel line to bit over bleeders.
A vacuum. (hose type)
And a fillet knife to cut foam.
Just heated up the can on the stove and pressed into foam to form a lip in the foam for the can to seal against.
While facing lip, cut a hole smaller diameter then vacuum hose. (hose will press into foam even with the hole being smaller and guaranteed a tight seal)
Cut a hole for fuel line and insert line to
bottom of can.
Seal up foam to fuel line with Gorilla glue. (let dry)
Fill like normal with bleeders open.
Pump break.
Wait for bleeders to show fluid then close.
Open one bleeder ( on dual disk), attach line to bleeder, open master, vacuum while insuring master is kept with fluid.
Wait for bubbles to stop.
Close bleeder.
Go to other side and repeat for dual.
Do not let the can get to much fluid build up as you want to keep fluid out of vacuum as much as possible.
Be sure to test your pressure for brakes before every ride
always regardless of working on the bike or not. (just a reminder to any newbies)
My vacuum cleaner contains next to none when it comes to metal parts.
Cheap china crap.
Would be less likely to use with a expensive model vacuum cleaner as the break fluid will cause damage to metal.
