I've bought the Geeetech prusa i3 pro B and there must be something wrong with my extruder (mk8) as you can ser in the picture below.

I have triad cleaning the Nozzle and the pipe which the Filament is fed through to the Nozzle. I have also cleaned the extruder but none of this helps. By the looks of it it must have something to do with either the gear which pulls the Filament down or the motor since the problem come and go periodocly.
Any ideas?