Hi,currently own a 1980 xs 1100 that i am having a similar problem with. I am the owner of a motorcycle salvage yard and i have replaced and gone through everything on the bike. and yet still cant get it to run right under a load over 5,000 rpm? its a mystery to us and the only thing we havent replaced is the CDI box. i am currently trying to locate another CDI box to swap out mine and see if this solves the problem.