Harley-Davidson throttle controls feature a pull-open cable and a pull-closed cable. This gives very positive control to the throttle position. The pull-open (forward) cable operates the throttle plate by pulling it open against the pressure of the throttle return spring. The pull-closed (rear) cable acts as a fail-safe by providing positive throttle closure if the throttle return spring is broken or otherwise incapable of closing the throttle when the pull-open cable is released. These cables must be properly tightened or they will introduce drag and resistance to motion in the throttle system because of cable bind.
Slide the rubber boots off of the throttle cable adjusters located near the middle of the cables. Loosen the adjuster locknuts on both cables with adjustable wrenches. Loosen the pull-closed cable adjuster a few turns before attempting to adjust the pull-open cable.
Roll back on the throttle grip to actuate the throttle. Observe the throttle plate cam where the throttle cables are attached at the carburetor. The cam should just begin to move after a few degrees of throttle rotation.
Loosen (collapse) the adjuster on the pull-open cable until enough slack is present to allow for this few degrees of rotation. Tighten the adjuster if too much slack is present and the throttle control feels sloppy. Tighten the adjuster locknut on the pull-open cable with the wrenches once the adjustment is correct. Verify that the adjustment did not change when the locknut was tightened.
Tighten the slack out of the pull-closed cable. The cable should be tight enough to just return the throttle to the idle position. Do not overtighten this adjuster or the cable and throttle grip may be damaged while riding the bike, creating an unsafe condition. Tighten the adjuster locknut with the wrenches.
Hold the throttle closed at the throttle grip and try to rotate the throttle cam by hand. Check that the cam tab that bears on the adjustable throttle stop displays a small amount of rotation to ensure that there is no cable bind when in the idle position. Roll the throttle back full and allow it to snap back into position. Lack of a snappy response indicates cable bind and the system will have to be readjusted.
