I want to personally Thank You for sharing you knowledge & experiences with China Girl motors. Your pictorials on Photobucket are informative & educational, as are the Google Documents you share online. On behalf of the collective community of motorbikers & enthusiasts here on Motorbicycling-dot-com, I extend gratitude & appreciation for your efforts.
Go forth & be Awesome,
Contrary to what some people believe, I feel that the boost bottle helps. This is not for speed but on the low end. After installing one we had to lower the idle down, about a turn or so. We couldn't believe either, that there would be a difference. I feel that the bottle has to match the engine cc...either a 49cc or a 66cc. Using Sch 40 for a 66cc and a dome not a flat cap the length of the sch 40 should be 3-1/8", using a flat cap 4-1/2". I have a very short hose, and I suppose that if you use a longer one you need to take that into consideration. There is no safety issues where to mount the bottle. Once I drill and tap the intake manifold, I grind off the nipple (at a angle in mine) so there is no protrusion into the passageway. When I have it where I want it I JB Weld the nipple in the manifold.
re: Boost bottles. What has been your findings about size related to engine displacement? Has the length of hose seemed to change much (assuming minimum needed to mount the bottle safely, maybe difference of a few inches). I saw on a long thread about bbtls how one rider said he drilled out the brass nipples inside passages to the maximum. I don't know if it would make much difference, but I suppose it could.