Riding a motorcycle is difficult enough. The skills needed to drive a motorcycle can be much harder than driving a car or truck. A motorcycle operator has to concern himself with balance, less protection, and road surface much more than a car driver. Consuming alcohol prior to operating a motorcycle makes operation even more difficult. The National Highway Traffic Safety Administration sponsored a study in 2007 of the effects of alcohol on motorcycle riding skills. In the study, basic riding skills were assessed on a track with scenarios from the Motorcycle Safety Foundation's training program. In this study, riders were given alcohol and asked to perform basic tasks.
The study found that the effect of alcohol (between .05 and .08 BAC) on motorcycle operators was modest except when task demand was high, time pressure was high, and tolerances were constrained. Riding a motorcycle in real life includes high task demand, high time pressure and constrained tolerances.
If you are going to ride a motorcycle, be sure to do it sober to avoid serious personal injury.