TXT Boy 50 brake questions

[mrjoshua]

Hi all - I've just had a pretty rough TXT Boy 50 given to me by a friend who couldn't get it running but decided his kids wouldn't ride it anyway and it needed a lot of tidying it up.

I've got it started and running now fairly well, and am cleaning it all up, but the brakes a bit of an issue.  

All the pistons on both calipers were pretty stuck and I managed to free them off eventually, and luckily the pistons & seals were all in good nick, just I think it was all dried out, and some of the fluid had turned to thick pasty gunk.  I've cleaned them all out now, and am trying to bleed the rear setup but it just does not appear to be able to get any pressure in it for some reason, ie I've run loads of fluid through it but pedal does not firm up at all.

So I figured the master cylinder was in need of an overhaul and stripped it.  It was gunky inside, like the rest, but once cleaned thoroughly it's all good, and the piston & o-ring in it etc all look in perfect condition now they're clean.

When I open the bleed nipple on the caliper and press the pedal a little bit of fluid comes out, but if I nip it up and then work the pedal several times it makes no difference to the pedal, not matter how many times I've done the pedal>open nipple>bleed a bit>keep pedal down>close nipple>repeat sequence.

Have I missed something, or is there a particular way these ones need doing?

Don't know what year the bike is (is there an easy way to tell?), but the master cylinder at least appears to be a Brembo with the casting 4767.

I know the obvious thing to suggest here is to just buy a load of new bits, but 

1) as this bike is fairly scruffy and was free I don't want to spend tons on it, and 

2) The master cylinder all seems decent so can't really see that it'd help necessarily even if I got some bits to refurb it in all honesty.

Appreciate any useful help, thanks!
Jim

[mrjoshua]

BTW, the calipers are Hebo ones (not familiar with those) but I can't see any marking for a part/model number.  Both front & back are 4 pots, but what is a bit strange is the rear caliper looks to have had a dremel or something around the outside edge of it to enable it to fit in the caliper carrier.  Not sure why this would be needed unless either the caliper or carrier bracket were the wrong part for the bike I guess.

[dadof2]

Pressure bleeding is the answer. 10 to 30 PSI applied to the master cylinder will usually do the trick.

[mrjoshua]

Thanks for the reply dadof2 - I tried using a mityvac to vac bleed them but it just would not build any pressure no matter how much mucking about with it all.
I got a rebuild kit for the master and after fitting that and getting a load of the air out through the top, just working the lever slowly it then started to firm up and now has worked fine.

Interesting as the seals originally in the master cylinder looked perfect still but must have lost strength to push against the cylinder wall or something I guess.  Useful to know though that they can look spot on but just not work properly.
Am assuming the rear is the same as the symptoms of not getting it to pressurise at all are identical.