Find the Bultaco Manuel Solar site and you will find diagrams on there. There are some good photos on flickr as well. I had the same problem as you so I worked it out using these together.
hi pschrauber
I seem to remember you modified a clubfoot exhaust and had photos showing the inside modifications. do you still have them to share?
I did send you a message but you can't except them at the moment.
Many thanks
Noel