I’m coming to the discussion late, but back in the early days of shifters there were some Kawasakis (maybe others) that ran but then Honda became the gold standard thanks top SKUSA. But TJ is right — it’s just too small of a market for mfgrs to mess with. Honda Performance wouldn’t exist if it was just karting and not IndyCar etc. But look how many Yamahas have run in karting for home many DECADES and they haven’t gotten involved. Just isn’t going to happen.