Thanks ! .. there is probably the 'right' way to go about this, but as I really didn't know what I was doing, I just jumped in ...... with the shifting, I found there is some trial and error to get where you want to be .. first step is to find your baseline... spin it up on the stand (or take it to the street) and see what rpm/mph area it shifts...
Once you have the hub apart, you'll find a little torsion spring for the flyweights (there's only one in a stock hub) .. if you need minor shift adjustments (<3mph - approx.), you can get away with carefully bending the 'ears' on the spring.. if you need a later shift, you would increase spring tension.. earlier shift, decrease spring tension... if you need a much later shift (>3mph - approx.), then you can either add a 'second' spring to the other side of the flyweight plate.. or .. do what I did and try winding your own spring.. I got the some music wire that was slightly heavier gauge than my original spring, went on the web to see how to wind springs, and then made up a few .. if you wind your own, you'll need a sense of humor, because there is a bit of learning curve.. once you have made your adjustments (or springs), then it's back together, on the bike and test...
I almost ordered a bunch of different torsion springs that looked close from an online supplier, but decided to wind a few instead.. there is a German
SITE run by Jens Hansen who is a specialist on the Sachs hubs and also can supply some of the parts... if he has stock springs, I'd order a handful and experiment. .. I'm running a Sachs Automatic on the 700c bike, and also on a 451 wheeled
DAHON