My clutch is driving me crazy please help

[jeeves]

 Hello,
  I hate that this is my first real post... but here goes
I have 2009 Monster 1100 and on a 3000 mile trip this summer my Ducati performance slave cylinder decided to ingest some road crap and died a slow death in Kentucky.  I managed to limp back home (to Boston) by bleeding the clutch every 100 miles or so and replaced the slave cylinder with a new one. 
   Here come the driving me crazy part.  Now no matter what I do I cannot get my clutch lever to not lose pressure after a few days. I have vacuum bled and re bleed and flushed the fluid several times, and no matter what I cannot get the lever to hold pressure.  Even if the bike sits and is not ridden the air seems to leak in. 
  What is wrong here?  I have noticed that the rubber boot on the master cylinder has some wear from the clutch lever being used, but that must just be a dust cover for the master cylinder. I am hoping that I do not need to replace the master cylinder as well.  Those things are pricey.
Any and all suggestions would be greatly appreciated.  I am beginning to miss the reliability of my cable clutch Triumph.
 

[Speeddog]

Is it leaking brake fluid out anywhere?

I've had bikes that would suck air through a small split in the hose between the reservoir and the master, and also suck air past a bad grommet where the fitting is on the master.

[ScottRNelson]

I would also suggest looking at the master for the source of this problem if there is no obvious hydraulic fluid leak.

The clutch on my ST2 would go soft  after a week or two, but never quite bad enough that I couldn't find neutral while stopped.  I'm pretty sure that it needed new O-rings in the master cylinder to fix the problem.  The new owner said he was planning to rebuild both master cylinders on that bike.

[jeeves]

Thank you for the responses
   There is no obvious fluid leak anywhere, which is what has confounded me so much about this issue.  I am leaning toward the master cylinder as an issue as well.  Does anyone know if this is a rebuildable item? 

[ducpainter]

Thank you for the responses
   There is no obvious fluid leak anywhere, which is what has confounded me so much about this issue.  I am leaning toward the master cylinder as an issue as well.  Does anyone know if this is a rebuildable item? 

No rebuild parts are available for masters to the best of my knowledge.

That goes for all current production vehicles regardless of the number of wheels...the lawyers got involved.