A motorcycle headlight has one high beam and one low beam light. The rider can switch only one headlight ON at a time in most motorcycles.
As a result, either the low beam is ON or the high beam is ON. This gives the impression that the other light is not working. Especially in two headlight case arrangements.
While actually, both the headlights are in perfectly fine condition. You probably have seen the motorcycle running on the low beam with the high beam light turned OFF.
Giving an impression that the other headlight is not working.
Motorcycles having only one headlight ON
Many modern motorcycles have a headlight casing that separates the two lightbulbs.
The casing gives the impression that both these two lightbulbs should be switched ON.
But, that’s not how it works.
Most of the time, only one of these two lightbulbs is ON. And in some motorcycle models, only one can be ON.
Since only one lightbulb is ON, it creates confusion that the other light is not working. And if you have OCD tendencies, for sure this arrangement will drive you insane.
Yet, motorcycles having only one headlight ON is by design. And not an error.
The two headlights are not the same. One is a low beam and the other is a high beam.
At a time, the motorcycle rider will switch ON one of these two. Depending on whether the rider wants a low-beam light or a high-beam light.
High beam vs low beam
Let’s talk about low beams and high beams.
A motorcycle headlight has two beams – low and high.
The low beam is designed as a spread beam where the light falls close to the motorcycle and is wide in the pattern.
The high beam is designed as the long-distance beam which is narrow in pattern but lights up the distance far away.
Your motorcycle by default should be in low beam. It helps when you are navigating the traffic.
When you are traveling at night on a long highway road, high beams come in handy. They illuminate the long road ahead of you.
One key thing to note about the high beam. They are dazzling and obstructive to the traffic coming towards you. So use them sparingly.
Why not have both lights ON?
In most motorcycles, you can’t have both the low beam and the high beam ON at the same time. That is by design.
But in a few modern motorcycle models, switching ON both the high beam and low beam is possible.
Let’s discuss each of them one by one.
Motorcycles where both beams together is NOT possible
In many motorcycles, the two headlights cannot be ON simultaneously.
If you notice the motorcycle’s left side of the handlebar, you will find two things of relevance here:
- A headlight button
- High beam and low beam switch button
In many models, both these are clubbed into one single three-switch button. High beam ON, low beam ON, and both lights OFF.
Either way, you can’t have both the high beam and low beam lights ON at a time in these motorcycles. It’s an either/or case.
If you want to see the road right nearby your bike, the low beam is the way to go. And if you want to see far ahead into the path, the high beam is the best option.
In these motorcycles, manufacturers do not provide a way to switch both these lights ON together. You can switch only one of the high or low beams ON at a time.
Motorcycles where both beams together is possible
This is a minority as of now. Although their popularity is growing, it is still not common to see them.
There are modern LED headlight setups where you can have both high and low beams ON.
In fact, in these setups, the low beam will always be ON. And when you switch ON the high beam, both the high and low beams will be ON together.
The low beam is a constant in these motorcycles. At any time, the low beam headlight will always be ON in the motorcycle. The high beam can be switched ON or switched OFF.
So you have two kinds of light arrangements in these motorcycles. First, only the low beam ON. Second, both low beam and high beam ON. You don’t have an arrangement where only the high beam is ON.
It has always been like this
The separate low beam and high beam setup. It has always been like this.
When the motorcycle is on the low beam, the high beam light will be OFF. As a result, it looks like only one headlight is ON in the motorcycle. And the other is OFF.
The two-light setup is needed in a motorcycle.
Then, how come many other motorcycles have a single headlight?
These other motorcycles have different setups. But the low beam and high beam still exist.
First setup. The two different lights (one for high beam and the other for low beam) are packed within a single headlight casing. For us, it looks like a single light. But there are two different lightbulbs packed together.
Second setup. There actually is only a single lightbulb. The motorcycle headlight contains only one lightbulb. But, the lightbulb has two filaments. One for the low beam and one for the high beam.
The second kind of setup is very common in halogen headlights. They are called dual headlights. A single headlight consisting of two filaments.
You are noticing only now because of the modern setup
This one light ON and the other light OFF have become noticeable only because of this new setup in motorcycles. The casing or the arrangement has two separate headlights.
Earlier, either the two separate lightbulbs (one for low beam and the other for high beam) were stacked together in a single headlight.
Or, within a single lightbulb. Where there are two different filaments (one filament for the low beam and the other for the high beam). Again, these kinds of lightbulbs are called dual lightbulbs.
Why new bike headlights are always on?
Many regulations across regions and countries mandate that the motorcycle headlight should always be ON. Preferably the low beam.
As a result, many modern motorcycles have removed the headlight button altogether. You can only find a switch button to opt between high or low beams now. Or the low beam is a constant and you can switch ON or OFF the high beam.
The motorcycle headlight will always be ON.
If the low beam is mandated, the low beam headlight will always be ON. There will be a high beam switch to turn it ON or OFF.
If the low beam is not mandated, the rider can adjust between the high and low beams from the switch located on the handlebar’s left side. But cannot turn OFF the headlight.
The automatic headlight ON is a safety measure mandated by many regulations across regions. The motorcycle headlight should be ON all the time. Be it nighttime or daytime. The headlight should be running.
This is a safety measure. And the idea is to reduce motorcycle accidents, which are in high numbers. Hence the push for automatic headlights ON.
Taping X over the headlight helps the glass to stay together in case the headlight wrecks. It helps in easier glass removal. The practice came from old cafe racers riding on tracks. Nowadays, the X taping is more for aesthetics and to look cool.
These motorcycles have only one but dual filament headlights. A dual filament headlight contains two filaments – one for the low beam and one for the high beam. An alternative for two separate low-beam and high-beam headlights.
Dimmed headlights can be caused by various reasons including – battery problems, refelctor damages, blackened bulb, wiring problems, or wattage issues. We have a detailed post on headlight dimming here.