Aim the headlight

Home mechanic (basic tools) · Time: 20 to 30 min (estimate)

A headlight that points too low looks dim and shows you too little road. One that points too high dazzles drivers coming the other way. Check the aim after you change a bulb, fit an LED bulb, change the rear shock or its preload, or after a fall. Workshops include aim in a chassis tune-up and pre-delivery check.

Safety

• Do this with the engine off unless your headlight only works with the engine running. If so, work outdoors, never in a closed room: exhaust gas can kill.
• The bike must not fall on you: use level ground and a helper.

You need

• A flat wall and level ground in front of it, in the dark or in shade.
• The aim figures for your bike: the distance from the wall and how far the beam should drop. These are in your owner's manual or come from your local vehicle testing rules. This page gives no universal figure, because rules differ between countries and lamp types. The K-Light 125 manual we used does not give one.
• The headlight adjuster: usually one screw or bolt on the headlight shell or bracket for up and down. Some bikes also have a left and right screw.

Steps

1. Set the tyre pressures to normal: Check tyre pressure.
2. Park the bike on level ground, facing the wall, at the distance your manual or testing rules give. Point it straight at the wall.
3. Take the bike off its stand. Sit on it in your normal riding position (or have someone of normal rider weight sit on it) with both wheels on the ground and the handlebar straight. A helper holds the bike upright.
4. Measure the height of the headlight centre from the ground. Mark that height on the wall with tape, straight ahead of the lamp.
5. Turn on low (dipped) beam. Look at the bright top edge of the beam on the wall.
6. Compare the edge with your mark. It should sit below the mark by the drop your manual or testing rules give.
7. Turn the adjuster a little at a time. Watch the beam move. Re-check with the rider seated each time.
8. Tighten any locknut or bracket bolts you loosened. On a K-Light 125 the manual gives 10 to 12 N·m for the headlight mounting bolts and 37 to 44 N·m for the headlight bracket locknut. Use the value for the fastener you actually loosened.
9. Check high beam: it should point higher and further than low beam, along the road, not into the sky.

Check your work

• The top edge of the low beam is level and sits at the correct drop.
• Ride at night on a quiet road. You should see well ahead without oncoming drivers flashing their lights at you.

If it did not fix the problem

• Beam is weak even when aimed correctly: Headlight is dim.
• The beam pattern is blurred or spread out after fitting an LED bulb: refit the correct halogen bulb. An LED bulb in a lamp made for halogen often does not focus correctly, and in many countries it is not road legal. Check your local rules.
• The lamp moves when you ride over bumps: check the bracket and rubber mounts with Check chassis fasteners.

Reference values (K-Light 125)