I got a response from Mike from topkartparts.com link posted above:
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As far as I know, there is not a chassis manual provided by Top Kart and I am pretty sure I would know if there was one. There really isn’t much difference in how you tune a kart regardless of the manufacturer. The difference lies in the fact that different chassis like different rates of lift depending upon the weight, track and track condition. Even different Top Kart chassis like different setups.
What I have found to be most useful is a series of videos done by KRacers in Australia. They can be found at http://vimeo.com/kracer/videos and I suggest starting with the rate of lift video. It may not make total sense to you right away but as you look at the other videos, it will begin to do so.