My ValueJet prints a black line on both edges of the media, how do I turn this off.

The function is called "Flushing"

This is a firing of the nozzles on each pass of the carriage.

Go to  "Set Up" in the menu.

Here is a menu structure:
http://www.mutoh.com/products/ValueJet/VJMenu.html

Change "Flushing" from "On Media" to "Origin"

http://www2.mutoh.com/public/VJ-1204Operations%20Guide/eng/data/00000028.htm#VJ1204A_0801030000

or with pictures:
http://www.signwarehouse.com/support/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=414&nav=0,16,94

The nozzles will then fire on the sponge pad located near the right side of the machine.

Be sure to check and change the sponge pad when needed.
http://www2.mutoh.com/public/Manuals/User%20Operations%20Manuals/VJ-1604/data/00000034.htm#toc130