First replace the spark plug.  Then check all wiring connections for cleanliness and tight connections. 


!.  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. 

2.  If you are not getting any voltage at the feed wire terminal on the coil check the voltage from the source coil coming from the stator with the stator wires disconnected from the wiring harness. The peak voltage should be at least 100 volts.  I you do not have at least 100 volts replace the source coil and or wire that connect the source coil to the wiring harness.

3.   If you have 100 volts peak coming from the source coil on/from the stator, check the peak voltage coming from the pickup/trigger coil on the stator.  It should be at least 1 volt.  If you have 100 volts from the source coil and at least 1 volt coming from the pickup, replace the CDI box with a known good one.

4.  If you still do not have spark, check the wiring harness for continuity between the connectors.

5.   If you still do have spark start over you have missed something. 


The above test has worked on anything I have ever tested  that has a CDI ignition that is on dirt bikes, quads, jet skis, etc.  The above test voltages are also valid for these vehicles.

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.