I guess I don't understand that comment. Could you explain further? I thought you meant with the head taken apart.
Well, I took apart the extruder and heated it to 230 deg. and pushed filament through, but this was very difficult to do, way more difficult than with my UM original..
I did print .2 layers, 230C and it even ticks at 25mm/sec (printing a 30x30mm cube 100% fill) whereas my UM original can do 80 with ease..
So I took apart the feeder mechanism again.. and here are my findings; Aparently the filament is grinding into the plastic part which lead to friction.. this is caused by the sping being to strong/long and pushing the filament into the pastic part. Notice that this happens on both before and after the motor. Now I took the tension away, removed the nut and bolt and and now it prints fairly ok, 230c, 40-50mm/s, still not near the 90mm/s..
Here a photo of the grinded plastic feeder mechanism; http://s29.postimg.org/ikrztirzb/CIMG1392.jpg