http://www.ehow.com/how_7540775_measure-handlebars-motorcycles.html1.1
Place and hold a yardstick across the bottom center of the handlebars. Place the tip of a measuring tape on the handlebar at it highest point and stretch it down past the yardstick. The intersection of the yardstick and measuring tape is the rise, or height measurement.
2.2
Place a yardstick tip at the base of one handlebar and hold it level, pointing toward the seat. Place a measuring tape on the end of the same handlebar on the grip. Stretch the measuring tape down to intersect with the yardstick. This measurement at the intersection is the total pullback.
3.3
Measure the distance between the left handlebar to the right handlebar with a tape measure placed in the center and straight. The measurement is the center-width measurement.
4.4
Slide the grips off the handlebars with a pulling and twisting motion. Stretch a measuring tape from the outermost point on the left handlebar to the outermost point on the right handlebar, which is the total-width measurement. Replace the grips on the handlebars by pushing and twisting them on.