When buying a dirt bike, parts to check include the chassis number, rims, frame, radiator and brake pads. A used dirt bike should also be taken for a test drive.
The chassis number should be checked because if it has been scratched off, that indicates the dirt bike may be stolen. Rims should be checked for any damage or wear, such as cracks and bends. The frame should also be checked for damage. The radiator can be cracked or have bent cooling fins. A sign of heavy wear on the brake pads is grooves where the pads touch.
The dirt bike should be checked for leaks, including coolant or oil leaks. The dirt bike's cables and wires should also be checked for wear.
If a private party is selling the dirt bike, a buyer should also look at the condition of the area and any other vehicles the owner has. An owner that hasn't taken care of his other property may not have taken care of his dirt bike. The buyer should ask the owner how often he cleans the oil filter and changes the oil. Other important topics are the dirt bike's replacement and repair history, and if any modifications were made to it.