That's a tough job shooting the riders with the sun at their back, it puts their faces in a dark shadow. You might have shot from the other side of the road and used a flash to light 'em up. One reason is that they are probably going slow enough that you can get closer (safely) and two, it appears that they are looking around a corner to their left, so they would be looking more towards you than away from you. If you don't have your flash along, getting close in might allow you to get your camera to meter off their face and get acceptable exposure. Sure, your background would be blown out, but oh well!
Focus trouble? I dunno, some times I keep pressing the shutter half way down as the rider approaches to make sure I'm locked in before I depress all the way. I think that helps avoid catching on some tree branch in the distance instead. 
BTW, where's their helmets? 
Keep 'em coming!