Jerking problem with extruder

I have build a Prusa Mendel i3. When i extrude filament the extruder starts jerking around always at the same point of the big gears turn. Please see the attached youtube video to get good idea what i mean. [www.youtube.com] There is a small marking on the big gear to help you follow its spin. It starts jerking with that dot hits the driver gear.
What could be the reason behind this? I have tried different extrusion speeds and temperatures but they dont seem to affect the problem. Im really at lost.

Edited 1 time(s). Last edit at 06/30/2014 11:18AM by eripaha.

I would guess that either your big gear isn't perfectly round, or you've got some malformed teeth on there. I had similar problems where the little ridge on the outside of the bottom layer was grinding into the small gear, I had to clean that off all the teeth before it would run smoothly. Also, have you checked the current on the extruder stepper motor? If that's low then it might only take a small imperfection to stall the motor.

Problem was that i had tightened the Extruder Idler tightening screws too tight and i also had to reassemble the whole extruder.