Fire your "mechanic". It sound like he is making guesses as to your issues and will cost you big $$$ with doubtful results in the end.
If it were me and I was unable or not willing to do the work myself, I would find a way to get the bike to MurrayF for repairs. He knows these bikes.
There is a ton of help here to guide you thru fixing your bike. Other CDI's include the Ignitek (sp?) and the new Rae-San units.
No offence intended, but if you are unable to maintain a 35 year old bike you probably should not own one. Not many mechanics today have ever seen one, let alone worked on one!
Checking the main fuse is always a good idea, but on a stock CDI bike it has no bearing on running, once started as the CDI system runs on its own coils independently of the 12 volt system.
If a TI bike or a CDI bike running an ignitech or raesan ignition it is a factor. The CDI replacement ignitions run on 12 volt DC.
Should definitely run the stator tests and while running the chart test pin 9 for continuity to the three yellow charge wires. Continuity here can give some strange symptoms.
Rebuilding Handlebar Switches
Rider 81 500C, Thingy Born a 78Z. Ozdeluxe born an 80 shadow.
GET A MULTIMETER RTFM I am a CX500. If you maintain me I will run forever.