A two-speed inertia motor having a pair of wheels secured to a common axis, one of the wheels being a drive wheel and having a gear portion coaxial therewith for selectively coupling to an inertia wheel through a first or second gear member for providing two-speed ratios between the rotation of the drive wheel and the inertia wheel. A main gear member is coupled to the drive wheel, the main gear member having a splined shaft portion for slidably receiving a clutch member for concurrent rotation therewith, the first and second gear members being freely rotatable on either side of said clutch member. Means are provided for shifting the clutch member into locking engagement with either the first gear member or the second gear member to secure the so-locked gear member into direct coupling relation between the drive wheel and the inertia wheel. The drive gear is coupled to the drive wheel to provide slippage therebetween in the event of successive torque being applied to the drive wheel to energize the inertia motor.