60-65mph, more than fast enough to die. My official time on a 1977 XR-75 was 54mph, and that was on a dirt track.
I find the "organ donor" jokes tiresome and offensive, especially when considering 70% of all motorcycle fatalities are the fault of the automobile driver blocking the motorcyclist's right of way (according to the Hurt report).
The more up to date C.O.D.E.S. studies offered for public consumption twist the facts around in their zeal to push for a national motorcycle helmet law. When you clear away the window dressing, the C.O.D.E.S. studies are merely reaffirming the same conclusions arrived by Harry Hurt back in the '70s. The vast number of motorcycle fatalities are caused by the same old tired reasons; drivers in cars violating the motorcyclist's right of way. Any rider with ten years or more riding experience will tell you this is happening at an increased rate than before.
To be sure, a significant number of inexperienced riders do not have sufficient collision avoidance skills to avoid these scenarios, collecting themselves in Oscar Grope's fender or door or quarter panel. In a panic situation, the inexperienced rider's front brakes are typically underutilized and he or she actually turns into the path of the oncoming vehicle instead of away from it because they don't fully understand their motorcycle's steering dynamics.
As in the '70s, unlicensed motorcyclists (bereft of any formal rider training) are overrepresented in the aggregate data. It is also still true that states with mandatory helmet laws have a statistically higher motorcyclist death rate than states which do not have mandatory helmet laws.
One final point: It is usually the clinically dead helmet wearer that becomes the organ donor, because the brain activity helps keep the organs fresh and viable. The brain-dead biker is usually consigned to bone and tissue donations only, as the organs are usually not viable.