Try setting the preferences within the the motorcycle activity profile. Edit>Options>Activity Profile>Motorcycling>Routing. Set to Faster Time, turn off any Road Type Avoidances and turn off Feature Type Avoidances except perhaps Cable Cars, Narrow Trails & Climbing Paths.
Then, when creating a route be sure to use the Motorcycling activity profile. Use enough via points to direct the route to the roads you want.
There is a great BaseCamp Tutorial on the New England Riders webpage you may want to download: http://www.newenglandriders.org/Learn_BaseCamp.htm