Will a Motorcycle Start with a Bad Rectifier?

The answer to this question is both complex and straightforward. In essential terms, a motorcycle won’t be able to start with a bad rectifier—that’s it. But the actual question is: Why would a motorcycle not be able to start with a bad rectifier?

This question is like an onion. To know the answer, you need to ask another question and keep going until you have all the parts unraveled in front of you. But don’t worry, I will dissect each and every aspect of this question and explain it in layman’s terms in this article.

What is a rectifier and what is its use in a motorcycle?

The primary use of a rectifier is to convert Alternating Current (AC) to Direct Current (DC). It converts high voltage energy into practical work. That work goes towards charging the battery while it is in motion. 

AC changes its direction periodically. This is thanks to the alternator that is installed to generate electricity using the power of the engine of the bike. AC is suitable for transportation purposes, as it has low power loss and high efficiency. But AC current cannot be used in the form that it is; it needs to be converted to DC.

Headlights, dashboard, auto start, etc use DC. The energy is usually stored in a battery of some kind, which then powers the above-mentioned electrical systems.

It is advisable to ride for some time if your bike no longer auto starts. If the battery dies, you need to restart the bike manually and then ride for a few hours to recharge it. The rectifier is what helps it get charged up.

The way the rectifier does that is not very complicated but complicated enough that we won’t be showing it here. But, I will explain the way that a rectifier works.

The engine is connected with an alternator (a generator of sorts) that generates alternating current. This current cannot be used directly by the battery, which is why it needs to be changed to direct current first. 

A rectifier makes the required changes (smoothens it, rectifies the energy), making it usable for the systems. But what if I race some young punk and end up creating more power than the rectifier can handle? 

A rectifier is also connected with a regulator that keeps the voltage in check. It regulates the voltage and does not let it exceed the threshold limit. Hence, your bike also gets the same amount of energy no matter what.

Role of a Rectifier

A motorcycle can be started with the click of a button. But that is only possible through the series of connections that have been done behind the dashboard. But, to finish the circuit, an external push is required- provided by the rider in the form of pushing the button. 

When you push the button, it completes the circuit. A small charge passes through the circuit, causing the motorcycle to start. That’s why you need some charge in your battery even if you haven’t ridden before.

Therefore, the rectifier, the regulator, and the alternator need to make a good combination. Only if they are in synergy can the actual performance of the bike come to force.

Battery Low

A bad rectifier, on the other hand, can cause a slew of problems. If you have a bad alternator, the energy generation itself would be stopped, and you would know about that cause all the system will be burnt out within a ride.

But if a rectifier is damaged, it will not hinder the conversion of energy. So, each time you start your bike, the battery will be charged at a slower pace than before until the power demand finally outstrips the supply, causing the battery to drain out. In such instances, you need to either recharge the battery and change the rectifier or change the rectifier and start the bike manually, allowing it to charge once again.

Dead End

Yes, having a lousy rectifier can now seem like a bad idea. It will actively hinder your biking experiences and you could end up stuck in situations that could have been easily avoided.

To save yourself the trouble of having to replace a rectifier – or worse yet, a battery – you should have periodical check-ups of your bike done. They will not only keep your bike in perfect condition but also pick up on any anomaly before it has time to cause any disturbances. 

If you have the required skills and tools, then changing the rectifier at home is possible. However, keep in mind that the rectifier is an electrical component, and hence, does not follow the direct rules of mechanics.


So now we know why a bad rectifier wouldn’t start your bike. While it is not directly related, the domino effect is significant enough to cause the disruption, thereby causing the whole operation to shut down. All because of a tiny part.

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