Liability will depend on the circumstances, but typically if the other driver was responsible, they will be liable for the damages. Basically, if a state uses a fault (tort) system, the driver responsible for causing the accident covers the victim's damages (or at least, their insurance company does).
Keep in mind that motorcycle accidents can be caused by a number of things such as:
Dangerous road conditions
Weather conditions (motorcycle riders in Iowa know all about this one)
Poor traffic conditions
Faulty bike parts
... and much more.
Speaking of which, did you know that even in a single-vehicle motorcycle accident, others may be held liable? For example, the motorcycle manufacturer may be held liable for defects in the machine or the local or state government may be liable for hazardous road conditions. Again, every case is unique so it's important to understand all of the facts of a case for the most favorable outcome.
If you have follow-up questions, send 'em our way.