I would like to learn how to blur the wheels a little and keep the rider in focus. Nice photo =]
You need to have the right shutter speed for the conditions. "The conditions" is fairly encompassing, taking into account the speed of the motorcycle, the angle, the distance to the motorcycle. Ron's shot was made at 1/2000 second, a speed fast enough to freeze the front wheel's rotation with the motorcycle at that speed and angle.
When shooting digital it's a matter of estimation and experimentation. Slower speeds like 1/640 or 1/750 or 1/800 or 1/1000 might be needed to give just a tad bit of blur: the exact speed depends upon several factors. It might be that 1/1250th of a second is needed; if the motorcycle is moving at 55 mph it might be 1/640, but if the motorcycle is moving at 90mph, you would need a faster speed; this type of shooting situation is one in which the ability to instantly review your results on the back of a digital camera is extremely valuable.