Walk-Behind Mowers

I just used my PoulanPro PR675AWD all wheel drive for the first time. Is it possible to adjust and/or lengthen the cable that engages the drive? I can only move the lever about an inch before the mower starts to take off. It is hard to keep up with mowing around trees and my hands are sore from trying to move slowly while being spread so far open. I noticed some sort of coupling in the middle of the cable but I am not sure that if I attempt to adjust it that I would do any good.