How To: Magneto testing
When the magneto is ready for testing, there is a simple method you can use. Attach some rubber hose to the drive end of the armature with a hose clamp, then insert a metal bar in the other end of the hose with another hose clamp. Spin the metal bar with your cordless drill or with a lathe. Don’t forget to ground the plug to the magneto chassis with a bit of safety wire.
You can advance and retard the timing, vary the speed, check for spark with large plug gaps, run at elevated temperatures… It is all pretty easy to do on the bench, without building up the entire motorbike and getting it running.