They don't have an official change over procedure because it is technically not recommended to change over even though Mimaki does give a little info on how to do it. You have to trick the machine into being a CMYKx2 setup. The first step is to flush thoroughly. In my experience you have about a 50/50 chance of either the white, the silver or both will not flush successfully and will not print a full nozzle check once you have finished the whole procedure. This would result in needing a new head. If you are prepared for that then give it a go.
You want to use the, "Discharge and Wash" function, located in the maintenance menu, to flush the machine. This requires 8 washing cartridges and I would not recommend going with anything other than OEM if you want to do it successfully. It will empty the machine of ink first and then ask you to install the wash cartridges. It will then flush the machine. When it finishes, it will ask to re-wash and you want to do that at least 2 more times for a total of 3. This will most likely use the whole cartridge.
Once you get done with the 3rd wash, check the ink lines and see if you can see any ink left. You will probably see little bits here and there but you shouldn't see large solid areas of ink line full of ink. If they look good, it flushed well but the head could still be clogged partially so you aren't out of the woods yet. This is where I would change the dampers and install the H connection for the CMYKx2 setup. If there is a large amount of ink still in any of the channels, the head is clogged and is going to need some work or be replace all together. It is also a good idea to start this procedure with a new cap top to be sure you get the best suction. Also make sure the pump is not clogged before starting.
Once the machine is flushed and the ink lines are configured correctly, you need to change a few parameters. Turn the machine off and then turn it back on while holding the left and right arrow keys. This gets you into parameter input mode. Scroll down to find, "Custom Parameter" and hit enter. Then scroll up until you get to parameter 95 and change it to "0". Hit enter and then scroll down to parameter 96 and change it to "1". Hit enter and then end to go back. Now scroll down until you see, "Running Parameter" and hit enter. Scroll until you find parameter 120 and change it to "0" and hit enter. Now scroll down to parameter 121 and set it to "0". Hit enter and then once the parameter updates, power off and turn the machine on again in normal mode. It will ask which type of ink you are using and which color set. Just choose the correct ones and then it will prompt you to install the cartridges and pump the ink through the machine. Watch the H connection to make sure it isn't leaking due to bad o-ring etc. Once it's inked up, do a test print and see how lucky you are.
