When I raced bikes with motors I always felt confident until I hit triple digits. I was fast on a slow track and slow on a fast track. Some of us fear speed more than others and for good reason. There is simply less reaction time for a correction. Without the confidence in ones abilities you already have two strikes against you. I managed to escape without serious injury.
Labor Day weekend I was riding my bike(motor) up a hill to my home, going about 10mph when I hit some gravel and was thrown off. I now am laid up with a recently repaired rotator cuff.
I don't mean to generalize but when you remove two of the four wheels you are taking chances - but everybody needs a hobby.