How To Troubleshoot & Test The Ignition System On Your 1994-2001 Yamaha YZ125
Electrical troubleshooting can get very frustrating, and it’s very easy to lose track of what you’ve done and still need to do, so write down everything you need to test, then as you go, write down the test results.
You want to start with the simplest solution; there’s no sense replacing the stator when all you had was a ground fault.
So start with the spark plug, then work your way back to the stator.
You can only test the CDI through the process of elimination, so if everything else is tested within spec, the CDI will need to be replaced.
For whatever reason, Yamaha does not provide peak voltage specs for anything, so If you want to do a physical test of your ignition coil, you will need to take it to a shop and have it tested.
Here’s a link to open the YZ125 Electrical System Specifications in a new window.
You will need a multimeter if you get to the ignition coil and stator. If you don’t have a multimeter yet, you can get one HERE.