Hi Mcguyver,

Indeed unfortunally Europe is a overcrowded place, especially western Europe roughly between the North sea / Baltic sea and the Mediterranean sea. July and august always have been the most busy months, both because the school holidays and the summer weather. September would have been a better month.
On a motorcycle you are a little bit better off then as a car driver because it is a bit easier to pass traffic and traffic jams.
There are some things you can do to escape the worst traffic tho. For example you could google ¨black saturday¨ then you will see when the most traffic is in and in which direction (north or south). This is especially true for transit countries like France and Germany.
Going away from the main roads and drive more through the countryside will also get you out of most traffic. As Mark said, avoid the most touristic places or maybe google those places you want to visit. It is well possible there will be some websites where you can see what the most busy days and times are.
I think you are not doing much transit but if so, for transit I would recommend driving at night. Driving in the mornings and relax at the hottest part of the day is also a possibility. You can also trying to find the websites of italian/croatian road administrations and automobile clubs. They probably have tips, advice and information.
In short: august is not the best month but it is not impossible.

Have a nice and save trip.

Rögnvaldur