XB model Buells and Harley-Davidson XL and XR models have the same approximate service intervals and requirements and procedures. Presently owning 3 XB's and 4 XR1200's and having serviced well over 100 of each model, I've found that the below will meet all your needs:
ENGINE: Capacity is 2.5 US quarts with full drain and filter change. Any quality 15W50 or 20W50 works fine. Full synthetic NOT required. Shop by availability and price-point. Drain time of at least 1 hour at both swingarm drain plug and filter housing. Replace O-ring on drain plug at first service...inspect closely every other service and replace if required.
TRANS/PRIMARY: Capacity is 1 US quart with full drain time of at least 1 hour on sidestand...tad longer on vertical lift. Primary drive system and transmission share the same fluid and it is NOT mixed or shared with engine fluid. Same rule of thumb on drain plug O-ring as noted above. My personal preference for primary lubricant is:
Mobil-1 20W50 motorcycle JASO-1....Amsoil 20W50 motorcycle JASO-1....Motul 20W50 motorcycle JASO-1...Harley-Davidson Syn-3...Walmart Supertech 20W50 V-twin motorcycle oil which is Mobil-1 posing as Walmart house-brand. Some use ATF trans fluid or 75W90 gear lube. I do NOT.
OIL FILTER: All XB filters same as 2007-2018 Toyota Yaris 1.5L. Use that cross reference when filter shopping.
Personal favs are Wix...K&N...Bosch...OEM.
SPARK PLUGS: NGK DCPR8EIX. Iridium and correct heat range. Pricey but worth the extra bit of cost. Noticeably better throttle response and longevity.
SPARK PLUG WIRES: OEM part # for set is Y0204.02A8C. Part # still active in dealer system. Option is to retain the coil and plug boots and wire end terminals...source new 6.6mm wire on your own...and build your own set on-the-cheap.
You're welcome.