If you have already checked and refurbished (if necessary) the oil-pump assembly, you should also check the oil-tank and the various lines, unions and filters that feed the oil-pump; replacing degraded, cracked or corroding parts with new components.
More oil tank assembly related components you may wish to consider:
Add as many items as you wish to the same shopping cart, new gaskets for example, and still only pay the same single fixed price shipping cost.
Please be aware that this component may have other applications within the Yamaha model range. So ensure the part-numbers you order are correct for your model.