For the past 20 years or so, motorcycles have been jetted not to produce optimum performance but rather to comply with the mandatory emissions regulations in effect during their year of manufacture. Consequently, they all have lean spots throughout their various fuel-metering systems, so they all could benefit from adjustments in the air-fuel mixture. There are a few aftermarket pipes available that give good results without any carburetion changes, but those bikes would run even better if they were rejetted.