Took in this route as part of a bike tour through Eastern Europe.
We filled a van with three Gsxr 1000s and drove to Salzburg in Austria where we left the van for three weeks at a hotel.
From there we headed through Austria, Hungary, Serbia, Romania to the Black sea via Transfagaras. Then into Bulgaria along the coast before heading back inland towards Sofia and back into Serbia. As you head West to wards Visegrad in Bosnia, the roads open up and the terrain is mountainous with fantastic scenery around every corner. This is probably the best route Ive ridden, it has distance (approx 100 miles of rolling roads) and the road surface is fine with little traffic and inoffensive police patrols from time to time.
Make sure you stop in Visegrad for lunch by the the river Drina and the famous bridge (google ridge over the Drina)
The descent into Sarajevo is just as fantastic, passing through small villages en route. Sarajevo is a great mix of history and culture and worth stopping for two or three days to really take it all in.
When you leave, to the west, the terrain starts to flatten and you can stop at Mostar to see another classic bridge!
Dubrovnik in Croatia is the next stop. Head north from here, keep to the ocean road, it gets better the further North you get!