I have a beta evo and having problems with the front brake, I have noticed that 2 of the pistons are not coming back out of the caliper, so deciding to rebuild it,

does anyone know how to do this

cheers

You may be able to get away with just cleaning the front brake caliper. Remember that the only things to clean the square section o-rings and pistons are fairy liquid with water ( cold ) and/or brake fluid. Be careful not to lose the wee o-ring between the two caliper halves. You will need to take care that the square section o-rings are seated properly in the caliper before re-installing the pistons and be careful you put the pistons back in true to the caliper bore. GOOD LUCK.

Red rubber grease for assembly.

Often the problem is corrosion build up in the seal grooves. Polish the grooves out with steel wool or rolled up very fine wet N dry paper. A dentists mirror (cheap on ebay) is useful for checking the grooves. Do not put rubber grease in the seal grooves.

http://www.redrubbergrease.com/tips-how-to-brake-caliper-failure-repair-with-rebuild-kit.html

Did mine not to long ago. Had to really work to get the old pucks out. Caliper showed the new ones were a few thousanths smaller. Cleaned the grooves and rebuilt the brake caliper with the new pistons. Now works perfect. When you rebuild it remove the caliper from the fork leg and pick it up by the bars, secure with a tie wrap then disconnect the banjo bolt. After rebuilding the caliper pour brake fluid into the banjo bolt hole to fill the caliper and attach the brake line. This makes the bleeding procedue much easier. Reattach to fork and bleed.

That`s great advice Dan, but it depends on the condition of fluid. I would drain it all if you are having problems. Contaminated fluid has no business in a rebuild. But I do agree refilling the caliper first.

You're right of course but I'm bad as far as flushing systems to change fluid anyway. I was surprised at just how stuck the original pistons were though and once the new ones were in the front brake is like buttah! Unfortunately the back is now sticking and I'm not looking forward to that rebuild.