What to do to a Froze up Master Cylinder?

[Meat-BoX]

I have an 86 Honda 200x and the rear brakes need to be restored. The Master cylinder is froze up and doesnt work. I have the whole system off the Trike and am just trying to figure out what to try to do to get her rebuilt. Anyone have any Tricks or Knowledge on the best way to free up this thing and get it all rebuilt or working? Thx.

[ATCWRENCH]

take as much of apart as you can and set it in a cup of brake fluid for a day or two. take it outta the cup and clean it with a rag, then hit it with compressed air. dont look at the piston when air is applied. bad things will result.

another way to go is to get some PB Blaster. its an amazing penatrant spray. use the same way as the brake fluid.

[Bryan Raffa]

I had to drill a hole in the alum. slave and use a screw to to pull it out it was in there good. i soaked it for a week comressed air works good if it not to bad dont worrie about the slave a new one comes in the kit ,dont mess up the walls of the cyl. or you will have blow by when the seals move up and down

[atc4everbob]

I have twice successfully done the same thing while rebuilding my 350x master cylinder. I also drilled and tapped (fine thread) the aluminum piston and put a bolt in it. I then put the master in a vise and used a 1lb slide hammer on the bolt. Two pops and it broke loose. I would not advise using a self-tapping screw. The threads may not bite well and just pull the aluminum material right out. You'll then have to drill a larger hole and try again. You won't have many opportunities to re-drill before you reach the inside diameter of the cylinder walls. Make the first try count! There will be a rust ring where the piston was seized. Use some very fine sandpaper in the cylinder wall to smooth the rust stain. I wrapped some fine paper around a large drill bit and used that. Worked great. Both rebuilds are still well in use. Good luck.