in the primary cover, you fool
You remove the derby cover (the large round cover on the left side of the bike) and fill there.
You should only use Harley transmission fluid from the dealership. It's engineered by Harley for their transmissions.
harley has their own suggested fluid. however many of us use the same oil in the engine, the tranny and the primary. 20/50
AMSOIL 20W50. Don't overfill.
The fluids I E oil is filled in the oil bag, DO NOT OVER FILL. The primary is filled by removal of the derby cover (the large cover on the side of the primary) and is filled only to the lowest point of the opening. I suggest finding out what fluid was used in the primary, I suggest using type F ATF trans fluid.
Harley recommends their own Formula+ but I prefer Red Line Heavy ShockProof gear oil. http://www.redlineoil.com/product.aspx?pid=44&pcid=8
locate and remove your primary oil drain plug, once the fluid is removed,remove the derby cover and replace the primary fluid to the approiate level
through the clutch inspection cover. The Primary and transmission share fluid.
a small screw on the primary at the bottom near the rear. Looks alot like a primary screw.
In as much as Harley has discontinued Sport Trans Fluid and it's now an obsolete part number I think the only HD product out there is Formula+ for your use.
adjust it correctly, use stock primary fluid and make sure the fluid level is correct.
20-50 wt motor oil OR HD Primary oil