Loosen the adjustment bolt located on the front of the right rear wheel by hand.
Tighten the bolt slightly after loosening it with your hand. Don't tighten the bolt too much.
Start the mower by turning on the ignition then move the control lever forward until the mower doesn't move forward or backward anymore.
Hold the lever in this position then turn the mower off.
Loosen the adjustment bolt while you hold the control lever in the same position.
Move the control lever to the neutral "N" position. Tighten the bolt securely. The linkage should now be properly adjusted.