Drive control for self-propelled power tool

A self-propelled, walk-behind power tool comprising:

• a power deck including a bed, an engine mounted on an upper surface of said bed and having a rotatable drive shaft depending therethrough,
• left and right drive wheels each being journalled on opposite sides of said bed for rotation about an axle, and means for connecting said engine to said drive wheels including a pair of idler pulley levers pivotally attached to said bed,
• a handle bar attached to a rear side of said power deck,
• left and right control handles operative to control operation of said left and right drive wheels, respectively, positioned on said handle bar,
• means for biasing each of said control handles to a neutral position, said control handles being pivotable from said neutral position to a drive position, and
• first means for moving each of said idler pulley levers at a first rate in response to a constant input to pivot each control handle from said neutral position to a first position intermediate said neutral and drive positions, and at a second rate in response to said constant input to pivot each control handle from said intermediate position to said drive position.