Motorcycle Repair: cb750f spark unit burned, regulator rectifier, honda cb750f

Question
Ive got a 1982 honda cb750f supersport.  The bike has about 30,000 miles on it. I was riding  down the road the other day when my main fuse blew.  I looked for a possible problem, and when I didnt find one, I stuck a piece of wire where the fuse goes so I could get home. After I started my bike I smelled something burning.  One of the spark units had melted, but the other was fine.  I disconnected the burnt unit and drove home.  when i got home, i removed the burnt wire from the harness that goes fron the spark unit to the coils and to the run switch.  The wire was black with a white stripe and it was the only wire that had melted.  I ran new wire, replaced both spark units and replaced the run switch.  The bike ran fine for about 3 days then it melted one of the new spark units.  Ive searched for a shorted wire, but i didnt find any.  What could be causing this problem?  Thanks for your help

Answer
Hi Wendel,

Sorry for the delay in replying. I've worked alot of overtime this week.

Check resistance of ignition coil primary and secondary windings. Compare readings with service manual specs.

Check resistance of plug caps and secondary leads.

Check regulator/rectifier for proper operation an d resistance values.

Check alternator output and check battery condition.

Respectfully,
Mark Shively