What’s the nozzle for and why is there a jet in the crankshaft bearing?

[Marqus]

Hi,

Can anyone explain what the nozzle is for, that sits behind the generator and sometimes gets scratches from primary chain?
And why is there a bronze jet in the lower crankcase half???



Thanks

[Pat Conlon]

There is an oil jet that directs oil onto the starter chain, is that what you're referring to?
https://fjowners.com/index.php?topic=19016.0

#23

[RPM - Robert]

Can anyone explain what the nozzle is for, that sits behind the generator and sometimes gets scratches from primary chain?

Pat already covered the nozzle jet for the starter chain.

And why is there a bronze jet in the lower crankcase half???

The oil "jet" is a restrictor Yamaha installed into the center main bearing journal. The reason I believe is that main bearing journal doesn't have any other function other than to lubricate the bearing, so it doesn't need as much oil as the other journals. Journals 2 & 4 provide the oil to the connecting rods. The right bearing sends oil to the cylinder head and the left bearing needs the additional oil to provide a more stable bearing surface to keep the crankshaft centered to control the ignition rotor movement.