I am not sure of viscosity, but if you have Harley Davidson on your fuel tank, you should use Harley Davidson lubricants. H. D. primary and trans lube or H.D. 20/50 synthetic motor oil will work just fine.
Knowing the year would help answer this better.
I understand you can use the same oil viscosity in both motor & transmission on the 2008 harley roadking!
1 quart of sport lube
20/40w
The primary oil does three things. Lube the clutch. Lube the primary chain . And cool the stator. If Harley thought Dextron would do this, they would have recommended the use of it. Keep your Harley a Harley.
HD recommends 20w50 in all three holes. oil, tranny, and primary.
The transmission and crankcase are one piece on a Sportster.
A 2001 Harley Sportster typically uses about 1 quart (approximately 1 liter) of oil in the primary chain case. It's essential to use the recommended type of oil, usually a primary chaincase lubricant or a specific motorcycle oil, to ensure proper lubrication and performance. Always check the owner's manual for precise specifications and maintenance recommendations.
On the primary there is a round (derby) cover. Remove the cover, fill until the oil tries to run out. Replace the cover. We use engine oil in our primaries.
It uses a special blend Tranny/primary lube.
For a 2006 Harley-Davidson, the primary case typically requires about 1 quart (32 ounces) of primary fluid. It's important to check the owner's manual or service manual for the specific model, as the exact amount can vary slightly depending on the bike's configuration. Always ensure to use the recommended primary oil for optimal performance.