The chart above shows the percentage of annual motorcycle deaths represented by the youngest age group (< 29 years) and the oldest group (> 50 years), according to annual data from the National Highway Traffic Safety Administration for the years 1975 to 2009.  In 1975, 80% of motorcycle fatalities were in the youngest age group and that percentage fell over time; only 3% of the deaths were in the older age group in 1975 and that share increased over time (see chart).  It's interesting to note that by 2009, the share of motorcycle deaths for the older group (31%) exceeded the share of deaths for the younger group (26%) for the first time ever.   

I assume these trends in motorcycle deaths reflect the popularity of motorcycles among the baby boom generation, who started driving motorcycles when they were younger and have continued to drive bikes as they age.  Meanwhile, if motorcycles have become less popular among young people in their 20s, the two demographic trends would explain why the share of motorcycle deaths represented by the 50+ age group is increasing, and was greater in 2009 than the younger age group's share of deaths.