My 14 RK has been using formula + in primary and trans since it was new and has 45k on the odo..... and the guy at the counter basically told me I'd be stupid not to use Harley's heavy gear oil .vs Formula+
No problems so far and I like how the clutch feels using the formula +.
The engine runs synthetic so I get lucas motorcycle oil or mobile 1 vtwin, which ever is on sale.
Napa auto sells k&n oil filters. (maybe a little cheaper than dealer?)