Here is a cool video of Gabrielle Gnani hand forging bar stock over a coal fire that ends up as transmission gears for his own built GP racer. He casts his own barrels etc. Plus interesting utility vehicles. Second video is the finished product from the rider’s seat. Wish I could understand Italian.
Note, there are 3 parts to the video of the construction of the bike. They should come up on the side bar on You tube.