Proper adjustment of a motorcycle's headlight is a crucial step in ensuring rider safety. During nighttime riding, a motorcycle's headlight is often the only available light source. If the headlight is improperly aimed, the rider will not be able to see the road ahead well enough to safely operate the motorcycle. Over time, vibration can loosen or break headlight adjustment screws, allowing the headlight to shift to an ineffective position. Headlight alignment should be checked often, and adjustments or repairs made promptly when needed. Adjusting a headlight is a simple task, requiring minimal tools and mechanical knowledge.
Refer to your service manual for the proper adjustment procedure for your make and model of motorcycle. Some headlights use knobs as adjusters, while others use screws. Some adjusters are exposed and easily accessed, while some are hidden and require long screwdrivers to reach. Whichever procedure your manual outlines, make sure you read and understand the procedure fully before adjusting your headlight. Find the adjusters in daylight, and remember where they are located, because making a proper adjustment is easier at night, when the headlight beam can be easily seen while shone at a distant surface.
Find a patch of level ground (preferably paved or concrete) in front of a light coloured wall or garage door. You will need to make your adjustment 7.5 m (25 feet) away from the wall or door, so the ground must be level between the two points. Measure 7.5 m (25 feet) away from the wall, and mark the spot with a piece of masking tape. When you make your adjustment, you will position your front wheel on the masking tape mark.
Measure the height from the ground to the centre of your headlight. On either the wall or garage door, make a pencil mark the same height as your headlight height measurement. Using a carpenter's level, draw a straight line across your pencil mark, and then align the top edge of a piece of masking tape with the line. This will be your reference point for adjusting your headlight's high beam. Make another mark two inches lower. Draw a straight, level line, and then align the top edge of a piece of masking tape with this second line. This is your low-beam reference point.
Sit on the motorcycle, holding it straight, with the headlight pointed straight ahead and the front tire on your masking tape mark. The low beam's upper cut-off line should align with the lower piece of masking tape. The high beam should align with the upper piece of masking tape. If the beams line up anywhere but dead centre on the masking tape lines, turn the adjusters as outlined in your service manual until the beams are perfectly centred and shining on their marks.
Ride the motorcycle, especially on bumpy roads, over train tracks, or any other rough surface that could jostle your headlight out of adjustment. Bring the motorcycle back to the spot where you adjusted your headlight, position your front wheel on the masking tape mark and test the light again. If the light is still positioned dead centre, then you are set. If the light has moved slightly, then readjust the beam, test-ride it again and retest. If the light has moved significantly, you may have a faulty or broken adjuster that will require repair.
Schedule regular headlight adjustment checks according to your riding style. If you take long trips, or ride often on bumpy back roads, check your headlight adjustment more often. Clean your headlight lens regularly. Dirty headlight lenses decrease the brightness of your light.
Always use a flashlight when locating your headlight adjusters in the dark. Electric shock is possible if you poke a screwdriver through the insulation of one of the many wires contained in a headlight housing. Only turn your ignition key to ACCESSORY when adjusting your headlight. Starting the motorcycle's engine is unnecessary, and can lead to injury if you accidentally engage the gearshift lever.