rd400 rear wheel brake sticking

[noonster]

Whats the best way to stop the back brake sticking on a rd400e,

I know how to check the basics, pistons,seals,floating brake movement etc

In the past ive put a double spring inside the master cylinder.

But ive heard its possible to drill the little hole in master cylinder a bit bigger this helps the return of the fluid better to the bottle.

Could this be right

[chrisg]

My guess would be the hole in the master cylinder. There are 2 holes, one probably 2mm and one about 0.5mm. I was told the best way to clear it is to get a single strand from a wire brush and push it through with some pliers. It cleared my master cylinder. Make sure you dont snap it in the hole, oo er misus, 
Has the callipers been refurbished? If left, they can become sticky.

Its always puzzled me that bikes have issues with brakes yet Ive had loads of cars, old and new, and never ever had a brake fault other that new pads or discs.

[noonster]

this is the rear brake pedal master cylinder, not the front,its different

[ajh]

Ive just been through it with my 250d twin piston rear caliper. Last year one side was sticky and this year its the other side. Just down to limited use over winter. I remove pads one at a time and work the piston in and out a few times with wd40 sprayed for good measure. Then take it on a ride using the back brake. Seems to work!

I can remember having to do it a few times on cars years ago but I was working as a mechanic so got through lots of cars