PLA doesn't come out from the extruder

Hello :) .
These days i had a problem trying to print with PLA. The printer start normaly, but in some minutes the PLA gets stacked and the filament doesn't come out. I tried rechanging the material and happened the same ... all normal but the filament stop 2 or 3 times per print, and i need put again the filament into the extruder. Off course the final print is not the better without some layers. 
Filament sounds like stuck but i was thinking that maybe is the nema 17 or the gear of the extruder, or the spool is so heavy (1 kg)
What's happening?
I bought this filament 3D850 PLA) and i tried this settings (attached):

Yes, is a motor problem. Somebody have the specific model of the Nema 17, for change it?