Bah, I didn't read all your post. Stupid me.

One thing I'd say to try checking spark is just unplug the lead a little and leave it on top of the plug. You should hear a pretty pronounced clicking related to rpm. If there isn't one or its not very loud there's a problem there.

The ignition module on the fender is a common fault in that engine but I think that will cause a no start issue or really random misfires

Do some snooping on here for cis troubleshooting too. Injectors are fairly common, fuel distributors have been known to cause misfires too.