I rebuilt the carbs back in may, had the timing set by a shop here in june, replaced a broken starter clutch in july and had planned to ride in august/september before the Western Washington winter made going outside generally horrible. Alas.
It was suggested to me previously (I think on the twins site) that the surging at 4K could be due to one of the coils not firing and since I really hated doing the carb rebuild I latched onto that as at least something new. The battery turns the starter over and fires up the bike but only once or twice and then it doesn't really like to. I am suspicious of the charging system because I have been able to ride it for some distance but if I stop it doesn't like to start again. But ultimately I have no idea. Being new to motorcycles, my diagnostic skills are a bit poor as yet. But every day I get the opportunity to speculate about something!
I did pop the cap to release the vapor lock, which worked once, but not the other times so while that may be a part of the problem, I don't know that it is the one solution.
Thanks for the replies