To fix electric scooter handlebars, first, make sure they are securely attached to the stem and check for any visible damage. Inspect the stem for any loosened fasteners or damage. If the bolts are loose, tighten them to the recommended torque using a wrench or Allen key. If the stem or handlebar clamp is damaged, you will need to replace it with a suitable one for your scooter's brand and model. Remove the old stem or handlebar clamp and carefully install the new one onto the scooter's fork and frame. Make sure to tighten the bolts to the correct torque. Finally, test the handlebars by operating the scooter and adjust them as needed.