I'm assuming you are referring killing yourself crashing a motorcycle. I've ridden and raced motorcycles for a long time, still ride but don't race anymore, I'm just to damn old now. I've had some pretty spectacular crashes, the last one just a couple years ago put me in the intensive care area of the trauma center for 5 days. I was really messed up. The engine threw a rod through the bottom of the case. Oiled the back tire and I highsided at speed. I was back on a bike 4 weeks later but took it really easy. I've had two other crashes that should have killed me in races on a track back when safety gear was not like today's.
That said, the body can take a lot of damage and survive. If you don't succeed at killing yourself you could end up being in a really bad situation. I know a couple guys that ended up in wheelchairs from accidents.