Not sure about all the DL650s but the early ones used a wheel speedo sensor, so changing the sprockets wouldn't make any difference to the reading. Later models may well be different. All DL1000s use a sensor from the gearbox so changing sprockets does alter the speedo reading, making it inaccurate. A smaller gearbox sprocket lowers the gearing, improving acceleration and increases engine revs at cruising speeds that you may not like. A bigger sprocket does the opposite, raises the gearing, reduces acceleration but can make cruising speeds more relaxing. Really depends what you are looking for. Generally speaking, standard gearing is best for most people.