Cleaning inside of old master cylinders

[drifter]

Well I'm finally running out of things to fix on my franken Pan, should be done in a few days.  So I'm thinking of my next project, the 1978 Sportster Cafe Racer I bought 3 years ago.  Quick history: the previous owner bought it in 1990, put the engine in a drag frame and rode it a 1/4 mile at a time.  Then put it back in the original frame about 4 years ago, got it to run and passed away.  The bike has brand new tires with a date stamp of 1990.  I have to go through it and fix a few things, one of which is the disc brake system (front and back) dried up and left crud in the cylinders and hoses.  I would like to keep the originals so does anybody know how to clean them out and make them serviceable again?  Any whiz bang chemicals?  I pulled the rear master off and managed to remove the piston, it fought pretty hard. 

[Pirsch Fire Wagon]

Disassemble, Parts Cleaner, Brake Hone if need be, If the fluid container itself has to be cleaned of scale, use a Dremmel with a sand Drum. let air dry and reassemble with new, reinstall.

[JW113]

Pine Sol and an ultrasonic cleaner.

-JW

[Don D]

No petroleum products should be used in a brake system to clean it.
Use denatured alcohol or fresh fluid. The cylinder itself can be honed with brake fluid for lubricant.

[JW113]

You could try alcohol in an ultrasonic cleaner, would likely do well if it's only gunk you're trying to clear out. If it's corroded, need something with a little more bite than alcohol. I like Pine Sol, it's water based, is a degreaser, and acidic enough to eat corrosion.

-JW

[drifter]

Thanks guys. 
I forgot that I have a brake hone, too many tools (NEVER!) bought over the years and stored out of sight, thanks.
An excuse to buy another tool (see above), an ultrasonic cleaner sounds interesting if I can find a place to put it, thanks.

Whatever the residue is that is in there is hard and dry, I was hoping for a magic elixir but will see how your suggestions work first.

[Don D]

Personally I would glass bead it then and then move forward with a flush and hone.

[Buglet]

   I would use plastic beads instead of glass and use a red scotch brite then a white one on a mandrill does a much better job then a hone.

[eglideic]

 I'm puzzled. Why is it not recommended to use "Brake Parts Cleaner" ??

[JW113]

When brake cleaner used to contain 1,1,1 trichloroethane, it worked great, but those days are long gone. These days brake cleaner is simply acetone in a spray can. Total waste of money IMO.

-JW

[eglideic]

When brake cleaner used to contain 1,1,1 trichloroethane, it worked great, but those days are long gone. These days brake cleaner is simply acetone in a spray can. Total waste of money IMO.

-JW

Thanks for the info. I guess being a chemistry professor like yourself does have its advantages.

[JW113]

Or, perhaps I paid attention during chemistry class.

-JW