August 17, 2014 11:34 PM PDT
I do not know for sure but I doubt that Harley makes much of their own parts. Most retail Car, Motorcycle, Peddle bike, etc. Buy from suppliers who specialize in certain products. GM probably over bought, or if they make their own gave Harley a good price, ignition switches and resold them to Harley.
I know Giant, my Street bike, is the biggest supplier of after market parts and frames to all the other bike manufacturers in the world. They provide all the aluminum frames for Specialized, Canondale, etc They are also the biggest supplier of disk brakes in the market.
So it is not uncommon for companies to buy parts from specific suppliers.