DC Motor inertia voltage drop
I've understood the problem: 
at what it seems Spice, if no argument is given, set a series resistance of 1 mOhm with the inductor, if a value of 0 is set for inductors series resistence the voltage across the inductor drops to 0 as desired.

Source: http://ltwiki.org/LTspiceHelp/LTspiceHelp/L_Inductor.htm