There is 2 way you can create it:
1 (top-down design): create a sketch that rapresent the primitives of rope and pulleys then create parts driven by the sketch. If you correctly dimension the sketch, changing it will update the parts.
2 (bottom - up design): Use an adjustable part for the rope and "crank" relationship to correctly drive it throu the pulleys. This could be a bit tricky at beginning cause you need to apply all the relationship correcly.
i made the rope and pulley model but know how to move the rope on pulley as chain moves on sprocket.