Step 1 - Warm up the vehicle by driving it for 5-10 minutes. This will help the oil drain more quickly. CAUTION - Exhaust and other parts of the bike may be extremely hot.
Step 2 - Support the vehicle on its centerstand.
Step 3 - The final gear case access is located on the left rear.
Make sure to place a drain pan in position, then remove the filler plug. I used an adjustable wrench for this, as I'm not sure what socket fits this plug. It's at least a 23 or 25 mm, which unfortunately I don't have. If not using a socket, take care not to damage the bolt.
Step 4. The drain plug is located on the left, at the very bottom of the gear case.
Remove the drain plug (10 or 12mm socket). It also contains a small aluminum washer, make sure not to lose this. If it is in any way damaged be sure to replace it.
Step 5 - Allow the oil to drain completely. You may wish to spin the rear wheel in reverse to ensure all oil has been drained.
Step 6 - Replace the drain plug and fill the gear case with the appropriate amount and viscosity of oil. The manual recommends:
150 ML of API GL-5 hypoid gear oil. When above 41 degrees F, use SAE 90. Below 41 us SAE 80. The manual also indicates a GL-6 gear oil may be used.
I opted for a multi-weight, 75W-90, Mobil 1, as I do plenty of riding in both kinds of weather.
If you were located in sunny CA you might want to opt for the higher oil year round. Use your own best judgment as to what kind of conditions you actually ride in.
Step 6. Replace the filler plug. Be sure to wipe up any stray drops of oil from your rims, and avoid contact with the braking system. Take the bike for a short test drive and inspect for leaks.
Final drive oil should be replaced every 7,500 miles, or more often depending on your riding style.