I would suggest using a synthetic motorcycle 10W-40 motorcycle specific oil and not a 5W-40 diesel oil like Rotella. You will get smoother shifting with a 10W-40 motorcycle oil. You don't run a motorcycle in winter time temperatures so the thinner 5W base oil has no advantages in a motorcycle but a few disadvantages - why motorcycle specified oils are never 5W.
I suspect the metals are from the oil immersed clutch plates.
Also change your oil as specified in the manual, usually every 12,000km or 7500miles and not more frequently, which is just a waste, especially with synthetic.
Heavier 50W oils in most water cooled Japanese bikes are just for Texas like summertime temperatures and never for close to freezing spring and fall temperatures, if you live in the northern US or Canada, 10W-40 works all season long.