yz 125

After riding motorbikes for a few months, I always wandered how do the companies make their motocross bikes. Do they make every part of the bike? Or do they order parts from different companies?
After doing some research on the motocross bikes, I learned that the companies order some parts from other companies and insert it into their bike. So when you buy your bike it has some after market parts in it and not all factory stock. When creating the bikes the company must plan and draw what they will do on a sheet of paper. After agreeing, they must get all of their materials. They start out with the framework using alum...