I have a simplicity sunrunner with a hydrostatic transmission. when i move the transmission lever forward the mower moves but the lever slowly returns to a slow crawl. the only way to keep it moving forward at a comfortable pace is to hold it there

Bix, May 2010

Most hydro units will have a friction pack on the side to stop this happening, if you follow the linkage from the hand lever down to the side of the gearbox you should see a nylock nut, under which is a large washer,a spring,and two damping washers, increase the tention on the nylock nut, this will increase the friction on the control arm and stop the hand lever from moving on its own.

Husqvarna man, May 2010