Qualcast 35s lawnmower, no progressive throttle adjustment? ?

My mower starts on the first pull, but appears to be racing too fast. There appears to be no progressive throttle adjustment as it continues at the same speed right the way through the adjustment on the throttle; of course as you reduce the leaver to it's lowest point the mower cuts out, which is fine. But, I cannot use the drive leaver as I am running after the thing! Again. I have no workshop manual.