I have a 1986 Honda TRX 250 Fourtrax and recently changed the starter, solenoid, and 12v battery. We got the starter to work but in the process we have been having spark issues where the plug gets fouled and we have to clean it every few days of operation. When we got done fixing the starter, we then had no spark.

We tried trouble shooting the no spark condition and started by replacing the plug, then the ignition coil, then the stator, then the CDI (however there are 2 boxes so I am not sure which one to replace...I think one is for reverse and one is for forward), then the pulse generator...all without avail. I also cleaned the main ground, thinking it may be a ground issue...still no luck. I need a way to methodically check where the issue is. I am a mechanical engineer...not an electrical engineer so I am only beginner at electronics. Any help would be much appreciated. Thank you,
Jeff