What bike do you have Yamaha frame number 48Y-021902?

The Yamaha frame number 48Y-021902 indicates that you likely have a Yamaha YZ125 dirt bike, which was produced in the late 1990s. The "48Y" prefix is specific to this model and year range. To confirm the exact model and year, you can cross-reference the frame number with Yamaha's official records or consult a motorcycle expert.