I ran across this on jumbojoke.com and even though it's meant for regular, mundane items, I thought they really should be applied to motorcycles. 

As scientists and concerned citizens, we applaud the recent trend toward legislation which requires the prominent placing of warnings on products that present hazards to the general public. Yet we must also offer the cautionary thought that such warnings, however well-intentioned, merely scratch the surface of what is really necessary in this important area. This is especially true in light of the findings of 20th century physics.  We therefore propose that the following list of warnings appears on every product offered for sale in the United States:

• WARNING: This Product Warps Space and Time in Its Vicinity.
• CAUTION: The Mass of This Product Contains the Energy Equivalent of 85 Million Tons of TNT per Net Ounce of Weight.
• HANDLE WITH EXTREME CARE: This Product Contains Minute Electrically Charged Particles Moving at Velocities in Excess of Five Hundred Million Miles Per Hour.
• CONSUMER NOTICE: Because of the Uncertainty Principle, It Is Impossible for the Consumer to Find Out at the Same Time Both Precisely Where This Product Is and How Fast It Is Moving. (Note: This one is optional on the grounds that Heisenberg was never quite sure that his principle was correct.)
  
• ADVISORY: There is an Extremely Small but Nonzero Chance That, Through a Process Know as Tunneling, This Product May Spontaneously Disappear from Its Present Location and Reappear at Any Random Place in the Universe, Including Your Neighbor's Domicile. The Manufacturer Will Not Be Responsible for Damages or Inconvenience That May Result.
  
• PLEASE NOTE: Some Quantum Physics Theories Suggest That When the Consumer Is Not Directly Observing This Product, It May Cease to Exist or Will Exist Only in a Vague and Undetermined State.
• HEALTH WARNING: Care Should Be Taken When Lifting This Product, Since Its Mass, and Thus Its Weight, Is Dependent on Its Velocity Relative to the User.
• ATTENTION: Despite Any Other Listing of Product Contents Found Hereon, the Consumer is Advised That, in Actuality, This Product Consists Of 99.999999999% Empty Space.