Don't know if 3 days is enough. It really depends on your route. Personally (and I'm from Germany), I think you can easily spend 3 days in the Black Forest only. No need to go to Munich. You'll get PLENTY of scenic rotes in the Black Forest. Try to go to the local Automotive Association office. They're called "ADAC". Members get maps (incl. specific motorcycle maps) for free there. And they might even work together with other associations, such as the RAC / AA.
Most ADAC offices are easy-going, and if you ask nicely, they'll probably give you all the maps you need for free! The best thing about the maps: They've got points of interest on them.
If you go in September, try to go to the smaller villages and ask for the nearest "Besenwirtschaft". It's restaurants ran by local farmers & they traditionally sell their own produce: wine, cheese, meat, bread. Absolutely delicious & authentic for that region. (They have a special license and are only allowed to open around the harvesting time, I think August - October). They might even have cheap accomodation in their farmhouse if you ask nicely. (Though I wouldn't count on that!)
Hope this helps