So, I have a little 50cc engine I've been working on. I made pretty good progress on it so far, and most of the stuff is working properly. It runs fine, but my dad told me I should test the voltage output of the CDI to make sure its working right. How do I go about testing this, and what voltage should it be outputting?
To test the CDI for output, you can readily check that the coil is firing before bothering with the CDI. If you get spark from the coil, the CDI is working. If no spark after removing the plug and stuffing it into the plug wire, grounding the metal of the plug on the engine and cranking(make sure the kickstand is up as some will kill the spark with kickstand extended), then check the voltage to the coil. The voltage to the coil comes from the stator winding for AC CDI systems. The CDI triggers the coil to fire by removing the voltage. You should measure voltage on each revolution of the crankshaft and flywheel. No volts may indeed indicate CDI failure, or it could be a failure in the stator CDI voltage winding. There is also a pickup that knows 'F' mark on the flywheel, and fires the coil by triggering the CDI. A spare CDI is a nice checking tool, but you can diagnose without one. tom