Sure, you might think that the White Scars are the fast-assault Space Marine force. But for me, when I think of Marines on Bikes, I think of the Ravenwing. In this preview from the upcoming Dark Angels codex, we get a look at the rules for running an all-bike army, as well as some of the other special goodies coming for the riders in black.
From the article:
The 2nd Company of the Dark Angels, known as the Ravenwing, are masters of the art of rapid assault, tearing across the battlefields of the 41st Millennium astride their jet-black vehicles. Like a flash of lightning before a thunderstorm, they form the vanguard of the First Legion’s many battle plans, carrying out vital reconnaissance and securing key objectives before the enemy has time to react.