Bleeding front brakes

[Amante_271]

Ive managed to get the front brake master cylinder from my GPx 250 and fitit too the trike as no sign of a brake lever yet. Problem is I cant get the system to pressurise to bleed it. There is loads of fluid in the reservoir, but when the brake lever is squeezed only a dribble comes out.

I know the cylinder was working fine on the old bike but virtually no pressure on the trike system. Any polite surgestions please as its got me and T.Bird totally stumped!!

Thanks

[FJ_Biker]

There is no quick way around this you will just have to keep bleeding

Good luck

[Amante_271]

Well we pumped and pumped and pumped until we got winkers (sp) cramp then eventually we started to get bubbles in the master cylinder... 1 or 2, then a few more, then loads! Eventually we got brake fluid squirting up in the master cylinder!! All over T.birds glasses and the front mud guard (Really good paint stripper! ) We remounted the lid as we started to get pressure building up and finally we could bleed the bleeding system!! [smiley=2vrolijk_08.gif]

I NOW HAVE A WORKING FRONT BRAKE!!! 8-) [smiley=thumbsup.gif]


WAHOO!!!! [smiley=2vrolijk_08.gif] Now the rear ones are begining to work as well!! [smiley=thumbsup.gif] Rock solid 1 min so they lock up then adjust and nothing!!! :-[ Not helped by the fact that the foot brake lever is bending! :'(

As usual 2 paces forward 1 back and 1 to the bleeding side!! ;D

[SupeRDel]

Its because you need to prime the master cylinder after having an empty brake system.

Simply pouring fluid in the top won't work (most of the time) - you pump away and nothing happens.

One way (not PC correct - recommend you protect skin and cover any paintwork well.

1. pour fluid in reservoir.
2. loosen banjo fitting and remove - fluid won't run out.
3. pull lever up to handle bar.
4. Place thumb over banjo bolt hole and seal it.
5. slowly release lever and fluid will suck into first part of cylinder where banjo fits.
6. replace banjo
7. cylinder is now primed - pump and fill - don't let level go below outlet in master.

[SupeRDel]

Rear brake master cylinder has a pressure relief hole near the main hole.

when you release brake it lets the pressure off pads so the wheel turns. This relief hole is very small and gets easily blocked up with crud in the system.

Its a common cause of binding brakes - a semi blocked hole will cause the pads to release a bit then they bind on the disc. Disc gets hotter - everything expands and the brake will lock on more

[6T]

thanks for the advise del and fj,not to up on hydraulic bike brakes give me cables any day ;D did do the thumb over banjo hole bit we then left it a bit and carried on with the rear brakes andrew just happend to pull the front brake lever in a little later and bingo we were able to bleed the system [smiley=happy.gif].the rear brakes are not motorcyle at all but the original reliant drum brakes most of which was completly shot we have fitted a new master cylinder and all new copper brake pipes new shoes and fittings the hydraulics to the rear are working fine we did have a problem with the shoes returning but there was also grooves worn in the back plates which i think was not helping,the shoes are now returning ok and its just a matter of getting everything balanced i suspect they have not worked for a good few years as everything was rusted and seized

[Dabz]

excellent news that you got it fixed! Sorry I wasn't much help, couldn't work out why the hell it was just pumping and pumping!

[jonnydangerous]

go to a chemist and get a plastic syringe, available in 10 or 20cc sizes, attach this to the bleed pipe, open the nipple and "Pull" the fluid through the system, keeping the master cylinder topped up! youll have no problems bleeding them this way, done it for years, wouldnt go back to the "Push" fluid through the system again!!!!!
binding brakes may indicate that the piston return/dust seal in the calliper is old and bloated. this is a square section seal that gets distorted slightly when you press the pedal, then returns to its original shape when pressure is let off. when they are old they bloat and cause the pistons to stick. easy to replace once the pistons are out, put new ones in with some brake fluid as a lube tho.......

hope that helps.

jaydee.

[6T]

thanks for the advise jaydee,have to remember the syringe tip the next time i do this [smiley=thumbsup.gif], i do have one i use for filling forks that would have done the trick.

[Iceman]

go to a chemist and get a plastic syringe, available in 10 or 20cc sizes, attach this to the bleed pipe, open the nipple and "Pull" the fluid through the system, keeping the master cylinder topped up! youll have no problems bleeding them this way
jaydee.

That's a useful piece of info.Need to bleed my brakes soon.Thanks for that! [smiley=thumbsup.gif]