Digital BW, The Print

Hi!
I have the MIS variabletone-Hexset and a few days ago, I made my first
Cool-tone print with them. The results are excellent except some small
amount of spilled ink on the upper right corner of the picture. It
comes from the "Yellow" cardrige. There is also some ink visible
underneath the glue where the tubes are attached to the cardriges.
After having read the MIS troubleshooting guide, I suppose that I have
lost the siphon break of the yellow cardrige. They say that you have
to print at least 50 sheets of paper without having the tube inside
the inkbottle to replace the break. Is there any other way to
re-establish it? What about a tiny hole at the open end of the
"Yellow" tube? Then it would be possible to pull out the ink with a
syringe and put it back into the bottle without losing any ink, or
could this procedure harm the cardrige?
Thanks 
Peter