Motorcycling is popular all over France in the summer, and there are many grand tours to be enjoyed. Motorcycling Brittany will have the most appeal to bikers who like days out that are a mixture of the bike and eating and sight seeing.
Main roads are good and have no tolls which makes getting here easy. Off the dual carriageways most of the A roads have good surfaces, and are twisty, with spectacular scenery around the coastline and the historic towns.
If you're never done it before you will be pleasantly surprised by how easy it is. You can expect fair weather and temperatures between 24-30c from June to mid September.
there are dozens of rides to do, but have a look here to get started.