Is a Yamaha yz450f street legal in Ontario?

No, the Yamaha YZ450F is not street legal in Ontario as it is classified as a Motocross bike, which is designed primarily for off-road use. In order for a motorcycle to be street legal, it must meet specific requirements, including proper lighting, mirrors, and registration. If you want to ride a YZ450F on public roads, you would need to modify it significantly to meet these regulations, or consider a model specifically designed for street use.