All Buell XB models are Harley-Davidson XL sportster and XR1200 engine/transmission architecture dating back to 1957. you're new to all of this so don't get confused by conflicting info.
1-your engine does NOT hold its own oil supply......your engine does NOT share its oil with any other system or component. XL/XR and XB have a dedicated oil tank to accomplish that. your "oil tank" happens to be your swingarm, as well. FULL DRAIN WITH FILTER CHANGE IS 2-1/2 QUARTS.
2-your engine drives your transmission thru a semi-wet clutch AND that clutch is driven by a large dedicated chain. the charging system alternator....chain....clutch are housed inside the large cover on the left of the engine assembly. THAT is what's known on these bikes as the PRIMARY DRIVE. incidentally, the device driving the rear wheel on these models is referred to as the secondary drive. make sense? the TRANSMISSION is housed in the rear of the 2-piece engine case assembly....BUT is completely shielded from same. the transmission shares ONE QUART of oil/fluid with the primary drive. that oil is poured into the primary assembly thru either the upper or lower removable cover. the oil then flows back and forth from the primary to the trans thru opening on left side of engine case.
the primary oil/fluid lubricates your transmission...primary drive components...and assorted ancillary bearings and bushings. it does NOT lubricate the clutch assembly. it only lowers its temperature and reduces annoying clutch plate chatter.