White takes some time and effort, once safe to print, not a bad idea to do some white-box prints on crappy media. Make sure your caps are flowing well, and circulation is doing its thing. If you want, mix of flush in with the white ink by siphoning some from the bottle station with a syringe and topping it off with flush. Might have some sedimented pigment in the head. If you have an old subtank (leave white lines disconnected), clip it on and use a syringe and some tubing to push/pull into the head. When removing the good subtank, make sure it is empty and keep it upright so the filter pads do not get contaminated with ink The little flushing elbow fitting can be ordered separately, or just use the one on the machine and flush channels 7 & 8 by pushing and pulling the solvent back and forth. Swap the flush out as it gets whiter and keep doing it until relatively clean. Your goal is not to push flush through the nozzles, it is to clean the passage above the nozzle plate. Gen5 heads have 2 input paths, one on the front and one on the back of the head for each channel. Most printers, these are connected together with a Y fitting, Mimaki leaves the port terminated with an air-bleed fitting (still not sure why). If you wish to push flush through the nozzles, be gentle and cap off both air ports (they give you extras with subtanks, grey termination clips) on the subtank and inject through the air purge port. When done, empty the head by pushing a bit of air through the line and the nozzles. After that, put the good subtank back on and do an air purge afterwards.