swapping a 1uf 200v axial capacitor for a .9uf 200v axial capacitor
Capacitors typically have rather a broad tolerance. There is little practical difference between a 0.9uF capacitor and a 1.0uF capacitor.

However, there may be some cases where the exact value of a capacitor is important. For example if this capacitor is part of the motor, you may not get full performance (time to start, torque, etc.) if the capacitor is too far from the design value.  

It would be easier to answer this if we knew exactly WHERE this capacitor is in the circuit.