First, check for any intake leaks or possible faulty sensors. Tuning should ONLY be done on mechanically healthy motorcycles.

Sensor data is largely dependent on the sensor environment. For example, in some earlier model stock exhausts, the rear sensor is positioned poorly. This ends up causing the cylinder to be leaned out when "tuned". The standard Harley motorcycle oxygen sensors are also limited by design. The sensor is designed to monitor AFR (lambda) to allow small real time adjustments in high MPG conditions, outside of those conditions, the sensor is unreliable and inaccurate. This is why Direct Link's AFR mode using the motorcycles sensors creates a temporary lean condition and target while calibrating steps are taken.

Remember, good data = good tune and better data = better tune. This is why many top tuners temporarily install external wideband sensor kits in ideal locations. These provide more accurate samplings at higher frequencies.