You might like to take a look at this post for the settings I used after you get the new insert for the Bowden tube... http://umforum.ultimaker.com/index.php?/topic/5739-175mm-filament-on-ultimaker-2/ You may need to tinker with the "Flow %" and the "Speed" slightly to get the settings that are right for your application.
Hi Conny I also purchased some 1.75mm filament and thought I would give it a try. I managed some limited success and managed to print a fairly decent Ultimaker Robot as a test. I set the filament size to 1.75 (as you would expect) and then set the "Flow %" to 150. But you need to slow down the printer head as it moves quickly to compensate for the added flow. I am using 55% speed (Which I set as the print is starting) I would not recomend this for long term use and I won't be using it unless it is a 3D printing emergency as I suspect the bowden tube is being over stressed. Good luck!