A key step in setting a Honda XR650R's suspension is found in adjusting the motorcycle's ride height. By altering the rear shock absorber's preload -- the amount of tension placed on the rear shock absorber's spring -- the XR650R can be adjusted to better suit the demands of the rider and the racetrack. In addition, setting the suspension's sag will ensure that the rear shock's preload is set up for your weight. Once the sag is set, further adjustments can be made to compensate for any changes in the riding conditions.
Place the your XR650R on an engine stand to relieve the tension placed on the rear shock absorber.
Loosen the locknut on the top of the rear shock absorber's spring with a hook-type spanner wrench.
Turn the preload adjustment collar, positioned between the locknut and the spring, with the spanner wrench. Turn the collar clockwise to decrease the spring's preload and lower your XR650R's rear ride height. Alternatively, turn the collar counterclockwise to increase the spring's preload and raise the motorcycle's rear ride height.
Tighten the shock absorber's locknut against the preload adjustment collar, using the spanner wrench.
Lift your XR650R off its side stand and hold it in a vertical position.
Measure the distance between the centre of the rear wheel and the bottom of the rear fender with the aid of an assistant and a tape measure. Record this distance on a note pad.
Sit on top of your XR650R while wearing all of your riding equipment. Have your assistant take another measurement between the centre of the rear wheel and the bottom of the rear fender with the aid of a tape measure. Record this measurement in your note pad.
Compare the distances from both measurements. The difference between the measurements is the rear suspension's sag. For example, if the first measurement provided a distance of 23 inches between the wheel and the fender, while the a 20-inch distance was measured while the motorcycle was fully-loaded, this indicates a 3-inch rear sag.
Adjust your XR650R's rear sag, as outlined above. Ideally, your XR650R should have a 4-inch sag for normal riding conditions, providing a well-rounded balance between maneuverability and straight-line stability. If the sag indicated by your measurements is greater than 4 inches, increase the preload to reduce the rear shock absorber's sag. Alternatively, reduce the preload to increase sag if it is less than 4 inches.
Adjust the preload, as needed, to compensate for the riding conditions found on your racetrack. Increase the sag by reducing the preload, to make it easier to turn on a shorter track filled with turns. Decrease the sag if you are riding on a longer track, filled with high-speed straight sections.
As a rule of thumb, decreasing the preload will lower the rear end, making it easier to place both feet on the ground while stabilising the motorcycle at higher speeds. Increasing the preload will raise the XR650R's ride height, subsequently enhancing the motorcycle's maneuverability.