Well based on my search's there is no yamaha it 475 in the ad is stated as a yamaha it 425 which is an actual bike. They are older bike's but are rare to find for sale as a full dirtbike. Parts may be hard to find but for a piston just take it to your local shop they can measure the cylinder and piston to tell you what size to get. These bike's go anywhere from 400-800 dollars in the shape this motor is in so the 600 asking price seems more then fair. You just need to ask your self if your going to actually finish it if you buy it. Also sorry in advance if this comes across as a db responce.