SW // Problem w/ motor assembly w/ flyingwheel and Motion Study

Good evening all,

I'm a newbbie on Solidworks 2017 and I want to use it to design train models. So probably my question is a dumb one. Sorry about it in advance.
I started with the core system for a train model ... the mechanical part, ie motor and mechanical components.
I designed the motor I would like to use as a first assembly owning the "stator" (just a mechanical representation of the external mechanical motor body) and a rotor (just a cylinder shaft). Both are "pieces" and put into th motor assembly.
Then I added this assembly into another one (one level above) and add a flywheel to the shaft (the flywheel is a component, not an assembly).
In the motor assembly (first assembly - without flywheel) I tested the Motion Study and I saw the motor shaft spinning - I added to motor shaft and flywheel a non mechanical slot jsut to visualize shaft / flywheel rotation (I don't care about speed or whatever else for the time being).
Then I tried also to make the overall assembly (motor + flywheel) spinning into Motion Study (Assembly4 file) but looks like I'm doing something wrong as the the flywheel looks like spinning only for a portion of the rotation, and the motor shaft doesn't spin at all ;-(

Thus I've some questions :
a) can someone take a look to the attached file and correct what's wrong to make in Motion Study both Flying wheel and motor shaft spinning together?
b) what constraint type should I use to make flying wheel and motor shaft coupled together?
c) can someone explain why when importing the motor assembly within a new assembly shaft in no more spinning in Motion Study (I used a "motor" simulator but doesn't help)?

Many thanks for your kind help and support.

Very Best regards,
Jeff BAILLOT