Utilising a reliable CDI setup and a standard 12v electrical system, the CB125E is pretty straight-forward - particularly being a single cylinder. Scroll down for the articles.
The ignition system is CDI, which means that it is powered directly from the stator rather than running on the battery's 12V output. One notable advantage of this setup is that even with a completely dead battery you can still bump-start the bike, which you can't do if your ignition box requires the battery's output to start.
Possessing but a single spark plug that's easily accessible, this engine makes it straightforward to check and replace the plug.
The spark lead runs from the ignition coil to the spark plug cap.
The spark plug cap sits between the lead and the spark plug.
This takes the output from the CDI box and turns it into high voltage current that's sent to the spark plug to create a spark.
This is where the ignition timing is managed; without it you won't have spark!
Replacing the headlight bulb is a fairly simple affair:
There are two bulbs of note at the rear of the vehicle - the brake light and license plate light.
Four in total - and simply to replace the bulbs on.
The gearshift indicator is LED lit, and shouldn't require replacement in the lifetime of the motorcycle.
Hopefully not something you have to deal with terribly often, fuses are nonetheless a very important part of the bike's electrical system. Without them you would risk damage to electrical components (or yourself) with wiring faults, as opposed to an inconveniently blown fuse. The CB125E has a number of fuses for different purposes in different locations on the bike.
If you aren't used to automotive wiring looms - also known as harnesses - they can seem quite intimidating at first. They are conveniently colour coded, however, which makes troubleshooting much more simple - you usually don't have to trace a wire along it's entire length to find where it ends, simply look for the matching colour.
This rectifies the AC current from your charging system, turning it into DC for the battery and 12v systems to use, and regulates the output so that it doesn't over/under provide.