brakes not bleeding
 

i recovered a discarded xt600... front brake master cyl. was siezed i cleaned everything out bled the brake had nice pressure but it would not hold because of a leak in the system, replaced hose and rubber diaphram and now its not building pressure it gave me a good bit of bubbles in the start and then completely stopped as if i got all the air out of the system but still no pressure. fluid does come out steady from the bleeder screws at the caliper but not as if it were pressurized. rear is having similar situation... i did have it sitting prior for a couple months with no fluid but still sealed up, is it possible my master cylinders need to be re-built?

Sounds like the seals have perished, you can get rebuild kits on ebay, it's not a hard job, just lube everything when you build it up.

I was going to say have a read of this topic on brakes then realized you was in that thread.

Inside the font master cylinder is there a white round plastic disk a the bottom? a mate had the same problem (as did i) and he removed the disk to bleed the brakes & it worked a treat. Not saying it will work for you but worth a try? another possible solution & a few guys had told me about was to remove the whole caliper, jam a screwdriver where the disk (rotor) would sit & hold it up level with the master cylinder, then bleed them.

Mezo.

@mike - ive made a visual inspection of the seals they seem to be in pretty good shape, also it squirts out from the master cyl. fine as if it were completely bled, i dont think it is the seals but i could be wrong

@mezo - now that you mentioned it i have heard of putting the caliper level with the reservoir i had actually forgotten about that until you said something will try that first.... ive not seen the plastic disk you speak of do you possibly have pictures or a diagram that could show me?

thanks for the help and the timely response

If it was passing the seals the lever would come back to the bars, does it do this?
Is it spongey or solid?
If it's holding pressure, have you tried tying the lever back overnight?

it does come back to the bars, its pretty spongey, but isnt holding the pressure it will momentarily grab then let off even with lever held in but i dont think the system is full its just not allowing me to build pressure in the system no bubbles even if the seals were bad i sould still get bubbles cuz there would be air in the line

If you look inside your reservoir you may see a dime sized disk at the bottom (where the fluid goes out) Danny picked out that disk & then bled his brakes easy, it must be a filter of some sorts? i dunno?

I didn't have a lot of luck raising my caliper, it did work for sure but i still couldn't get the firmness i was looking for, that was with a brand new master cylinder & brand new SS braided line.

I sold the bike with spongy front brakes & a warning to the new owner it needed looking at.

Mezo.

im going to have to look for this disk you speak of i tried raising the caliper and the lever was held in since we spoke last night and its still giving me the same trouble. im not even messing with the rear until i get the front worked out. thanks for the help. ill keep an update of the project.

It sounds like you may need new seals in the master cylinder.

ya thats what i was thinking just hoping not to hear