1.  Check the peak voltage at the feed wire terminal on the ignition coil where the wire from the CDI is connected.  (The wire from the CDI must be connected to the coil during this test.) The voltage should be at least 100 volts.  If the coil is good it will spark with 60 to 80 volts,  but not usually run good under a load.    If it is over 100 volts and do not have spark, replace the coil, or plug cap or spark plug wire. 

To measure peak voltage you need an oscilloscope or a digital voltmeter/multimeter with peak voltage capability or a peak voltage adapter that plugs into your voltmeter/multimeter.

If you do not have a peak voltage adapter you can make one for about $2.00.  Google how to make a peak voltage adapter.