Unfortunately it’s not that. I’m stumpedThat's the check ball for the oiling system. #27 on diagram. Make sure you have the check ball seat #26 and the spring #28 installed in the correct order.
Yamaha ATV 2016 OEM Parts Diagram for Oil Pump | Partzilla.com
I got the bike with the top end off and bunch of bolts in a magnetic tray and that was in there. The ball is 3/16 and the check ball is 3/8. I’m stumped, I’ve looked threw every schematic and watched several build videos and can’t see anywhere it could go. Starting to think it wasn’t a part of the engine. Previous engines the only other ball I’ve seen was for the clutch push rod but this doesn’t use one. Hate to do it but just gonna put it aside and fire it upWell, that's the only one I know of and it 's the same size?