Just read in the November edition of the Ulysses magazine, Ulysses is the biggest Australian motorcycle club with about 25 000 members, an article about riding in California. As already being mentioned by some before, the aussies also where full of praise about Dubbelju Motorcycle Tours and Rentals in Frisco. One borrowed a Triumph Tiger and the other one a Harley Sportster Low.
Here is the comment of Peter Thoemig, one of the leading motorbike journos here in Australia:I am happy to recommend them,their service is excellent.
Hope this helps, good luck.