The specific requirements for street legality of a dirt bike vary depending on the country and its regulations. In general, dirt bikes are not designed for street use and are primarily intended for off-road riding. However, some countries have provisions that allow for the conversion of certain dirt bikes to be street legal under certain conditions.
In the United States, for example, the requirements for street legality can vary from state to state. Some states may allow dirt bikes to be converted for street use, while others may not. The engine displacement or cc (cubic centimeter) size of the dirt bike is not typically the sole determining factor for street legality.
If you're interested in making a dirt bike street legal, it's best to consult the specific regulations and requirements of your country, state, or local jurisdiction's Department of Motor Vehicles (DMV) or equivalent authority. They can provide you with accurate and up-to-date information on what is required to make a dirt bike street legal in your area.