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What is a CDI Box on a Motorcycle? (Solved)

So you’ve had this odd-looking box sitting under your seat. It’s been there for years, but what does it do exactly?

A CDI Box, known as a Capacitor Discharge Ignition, allows a motorcycle to store energy for later usage, much like a regular battery, yet release energy almost instantly. The CDI is a trigger mechanism and is found on many modern-day motorcycles and determines when it’s time to zap the spark plug, while also being able to discharge capacitors.

Further more, a CDI box can control your rev limits and the timing advance surrounding your spark plug. In essence, it’s in direct control of your spark plug.

CDI Boxes Under The Seat

You’ve probably pulled open your seat and see those black box with some wires dangling from it. They’re almost always make up of the same gear: the box, some coils and a sensor.

Now – some motorcycles operate differently and may not use capacitors in the same fashion. The most popular alternative to a CDI is a TCI, though they operate very similarly and you can troubleshoot them pretty much without an issue.

CDI’s have been around for quite a few decades now and massively increased the efficiency of motorcycles, much like the advancement of fuel injection from the olden days of carburetors. They have fewer moving parts and generally are maintenance-free, but that isn’t to say they’re problem-free at all.

Dealing with CDI Problems

Some issues you can diagnose yourself and others you’ll need the expertise of an auto electrician. When it comes to spark problems with your motorcycle, the first point of call often is the CDI box.

You might have suffered some backfiring issues, cylinders which are dead, regular misfiring and really strange movements on your gauges. These are tell-tale signs that your CDI box is giving you issues.

Unfortunately, it’s not easy to trouble-shoot these and so we recommend eliminating all the other variables first. Or, as some riders like to do, simply order a replacement CDI right off eBay. These are relatively affordable aftermarket and their installation is quite simple.

You’ll find these CDI black boxes have numerous electrical components which do wear out after time. If you’re like many adventure riders and actually take your bike off the beaten track, then you’ll find that corrogated roads, moisture and heat certainly are strong enemies of many electrical components of your motorcycle.

Going Aftermarket

While you are replacing your CDI, do your research first and look for the best-in-class solution. The most reputable motorcycle dealers will have the best units available with warranties to last thousands of miles.

Not only will you have a new unit that will potentially last tens of thousands of miles, but you may get a mild performance increase. This is because some newer units alter the trigger mechamisn so it fires sooner and thus, you gain slightly more power.

There is much to learn about the engineering behind these units which you can find online. From Facebook Groups to Forums and countless YouTube tutorials, you’ll certainly find a good match for your make and model.

Who would’ve thought that such a small unit would make a massive advancement in how we operate our motorcycles?

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