What's wrong with my brakes, arrgghhh?

[soundbeltfarm]

Got an 07 RMZ 450 and the front brakes are giving me bloody grief.
i have bleed them twice now and they get nice and hard then about 3/4 way through trail ride they start getting soft and softer.
then they stay soft.
they still work but only to about half of what they were when ibleed them.
i can pull the lever into the grip.
it is a pain in the arse because when i need the front brake quick i pull with one finger and the lever hits my other fingers and i dont get ther stopping power i need.
when i bleed them i got no air bubbles or anything and thats been both times.
any ideas?

[sugilite:Me]

They can be blardy tricky at times. Things you can check are, make sure one of the pads is not rubbing the disc and overheating the fluid. When did you last change fluid? dot5 synthetic pick up moisture really fast if thats what your using. I'd suggest you check your crush washers, but as you are not getting any air, it's prob not the cause. Best place to start is prob total fluid flush and check for the pads rubbing, one pad would be a lot more worn if that were the case...good luck

[soundbeltfarm]

new fluid about 2 weeks ago.
it not dot 5
tried to flush backwards also with a syringe squirting it from the caliper up to the resovoir.
even wear on pads ( just looked)
also if it were them rubbing wouldn't it come good once fluid had cooled?
these stay the same once soft.
they still work but lever can be pulled back to the grip.
checked 2 other bikes , one like mine and a kx and they were awesome.
mine feels crap.
i use my front reasonbly hard too so it pisses me off big that they not working to their potential

[sugilite:Me]

Sometimes air can get trapped around the banjo joint where it joins onto the master cylinder? Do you think using the brakes as hard as you do could be boiling fluid?
Once fluid has boiled, the lever does not come back to full stiffness, not sure why.

[Sensei]

Your master cylinder may have a leak inside letting in air . Been new do a warranty claim on it Karl