79 KZ650 Loss of Power, Engine Quits

Make sure you check the ohms on your current coils and get the same rating

have you by any chance checked your charging circuit?

I had a similar problem and found that at higher revs my alternator was not charging properly.
The voltage at tickover was 12.5volts but only 10volts at 4000rpm.
the coils were not firing properly at low voltage

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I just had this exact same problem. The point condensor were hot soaking and failing causing the coils to fart out. Replace the points and condensers and problem solved