turned out to be condensor. I would set off and bike ran fine and after a wile it would start miss firing. Thought at first it was coils when they got hot, an old common problem on lots of jap bikes. I had changed condenser twice with new so never suspected. And strangely the condensor tested fine on bench. Anyway as it’s hard to get good condensor I thought of the usual electronic ignition but they can be a lot of money. After searching I found gammatronix web site. They do a electronic replacement for just the condensor and it still uses the points. I have installed and it purrs. I have had it running in the garage with the lights out and not a single sparks from the points.
much cheaper than full system and they quote, you should never need to replace points again apart from ware from cam.
i bought for four cylinder as it works out cheaper than buying for twin, then you have a spare.
hope this is of help.