I'm have having problems with my gas gas txt 2004 rear brake, i have bleeded the system many times and the brake works fine for the first ten minutes then all the pressure in the lever disappears and the brake doesn't operate at all, there is still all the brake fluid in the bottle so i'm guessing nothing is leaking or this would be empty, any ideas? thanks

Hi, have you tried back bleeding? If you have tried this then it sounds like the seals in the master cylinder have failed or if you`ve had it apart one of the seals may be in back to front !

Just a thought, are the pots in the caliper free to move ? Sometimes they can rust up or get full of crud. Worth a check.

id check the banjo bolt on the master cylinder.

if u got the one with the brake light switch incorporated into it then it will have a very small leak through the head of the bolt.

i have cleaned the pots and they move freely, the brake works fine but then just loses all pressure but the reservoir is still full, that's why i'm not sure what to do next.

If it did have a leak from the banjo bolt wouldn't the fluid drop in the reservoir? i have the cylinder with light switch incorporated?

Have you back bled the system ?

i have cleaned the pots and they move freely, the brake works fine but then just loses all pressure but the reservoir is still full, that's why i'm not sure what to do next.

If it did have a leak from the banjo bolt wouldn't the fluid drop in the reservoir? i have the cylinder with light switch incorporated?

bingo! i bet its leaking from there!

Try back bleeding it with a large syringe, they are tricky to remove all the air

i will pick one up this week and give it a try, take it you have come across the same problem?

No i haven't back back bled it what difference does this make to bleeding it through the reservoir?

i will pick one up this week and give it a try, take it you have come across the same problem?

No i haven't back back bled it what difference does this make to bleeding it through the reservoir?

yes, i had this problem with my bike.

i bled it to death until i found the (very small) leak. its very dificult to spot because of the location of it.

i got a new bolt and 2 crush washers from AB motorcycles for a massive £1.69.

it was there they told me that they see that problem all the time with that type of bolt.

cheers for the help going to replace the bolt and try back bleeding it, do i just attach the syringe to the caliper nipple, also where do i get a large syringe from?

cheers for the help going to replace the bolt and try back bleeding it, do i just attach the syringe to the caliper nipple, also where do i get a large syringe from?

Have a look on youtube, there should be a video, get the syringe off ebay 50ml or 100ml

Edited June 3, 201214 yr by Monty_Jon