black only in rasterlink pro II

[artbot]

i need to run black only on my 160sp.
the problem is it works for a small file but when i do a large file it's twitchy.

right now i am using a grayscale file. lots of solid blacks. color correction +25 on black.

it works perfectly on small files (10mb).

but on files around 200mb occasionally it will magically start printing purple-ish gray.

(the black line doesn't have black in it, i am just needing to isolate it as a spot channel. i'd use the two white channels but i don't want to contaminate those lines. black ink is kind hard to contaminate, and white is the worst).

so what am i missing? a little check box somewhere that will force this printer into black only mode.

any help would be much appreciated. this issue is frustrating.

 

[artbot]

also, if there are any spiffy tricks to get this printing to do a double cmyk print config for the black or 2 special color channels without having it set up for double cmyk that would be sweet. such as the double white channel should have the ability to run at double speed but in SS mode it just double prints at the cmyklmlc speed.