State laws differ on what is considered racing on the highway. In general though if two motorcycles are driving within the speed limit side by side it would not usually be considered racing just merely bikes driving beside each other.

However if the bikes continue to speed up together and are going above the speed limit then in some jurisdictions this may be considered a form of racing. You will need to find out your state's specific laws regarding racing on the highway to see if this situation falls within their definition of racing or not.

For example Florida's definition of racing or drag racing on the highway is listed under FL Statute 316.191. Here it states:

(a) "Drag race" is defined as the operation of two or more vehicles from a point side by side at accelerating speeds in a competitive attempt to outdistance each other, or the operation of one or more vehicles over a common selected course, from the same point to the same point, for the purpose of comparing the relative speeds or power of acceleration of such vehicle or vehicles within a certain distance or time limit.

(b) "Racing" is defined as the use of one or more vehicles in an attempt to outgain, outdistance, or prevent another vehicle from passing, to arrive at a given destination ahead of another vehicle or vehicles, or to test the physical stamina or endurance of drivers over long-distance driving routes.

The Florida law goes on to explain the penalties associated with racing on Florida roadways.

(2)(a) A person may not drive any vehicle, including any motorcycle, in any race; speed competition or contest; drag race or acceleration contest; test of physical endurance; exhibition of speed or acceleration; or for the purpose of making a speed record on any highway, roadway, or parking lot, and a person may not in any manner participate in, coordinate, facilitate, or collect moneys at any location for any such race; ride as a passenger in; or purposefully cause the movement of traffic to slow or stop for, any such race, competition, contest, test, or exhibition. Any person who violates this paragraph commits a misdemeanor of the second degree. Any person who violates this paragraph shall pay a fine of not less than $250 and not more than $500, and the department shall revoke the driver license of a person so convicted for 1 year.

(3) Whenever a law enforcement officer determines that a person was engaged in a drag race or race the officer may immediately arrest and take such person into custody. The court may enter an order of impoundment or immobilization as a condition of incarceration or probation.

To find out your state's definition of racing and if motorcycles driving side by side would be considered racing in any form check your state's laws and/or contact your state's Department of Motor Vehicles.