No pressure in front brake??

[OZSV1K]

Hey Techies, what am I doing wrong? Had to replace the front brake master cylinder on my son's DPro 125. Got a used replacement unit that seems to produces pressure in the "thumb over the hole" test. But.....once filled with brake fluid and bled, I get no braking effect, lever goes straight to the bar with no pressure?

Have tried two diffferent pistons - seal seems okay.

Wots going on?

Have ordered a new one from DHZ (who alway send gear really quick) but would like to have a working spare for the next time.

 

[sean01]

these can be tricky to bleed up..

the trick is you need to pull the lever in only like 3-5mm repeatedly. look in the fluid bowl and you'll see little bubbles coming out..
once you get all the little bubbles out you can then move on to doing full pull bleeds.

 

[rumble]

these can be tricky to bleed up..

the trick is you need to pull the lever in only like 3-5mm repeatedly. look in the fluid bowl and you'll see little bubbles coming out..
once you get all the little bubbles out you can then move on to doing full pull bleeds.

I had a bit of trouble with bleeding too.... 99% of the time it is air in the system, you just have to try everything to get it out. Tip the caliper up, tap it gently..... and that pulling the lever in quickly and repeatedly worked for me.

Also check that the lever is adjusted all the way out, it so it as far away from the bar as possible and can travel all the way.

 

[tim_]

there is also a tool you can use (stuffs me what the name is sorry).. it basically is a hand pump air vacum and you put that over the bleed bolt crack it and suck the brake fluid out until there are no more air bubbles in the brake fluid then re tighten the bolt... they are a god send it takes about 5 mins...

 

[OZSV1K]

:cursing:
Not a problem (for me) anymore as some pharkers stole my two bikes, my pushie and golf clubs last night (not that fussed about the sticks tho')

 

[shann]

i would be going berzerk!