I need to clarify one thing. The clutch and primary drive and transmission run in their own oil. You can use the Amsoil 20W50 V Twin synthetic in there, or something like Biker's Choice "Sportlube" Sportster trans fluid, Twin Power "Sportlube" available from any motorcycle shop that uses Tucker Rocky as a distributor. The biker's choice pt # XXXXX XXXXX and retails for $3.90 per qt., the Twin Power Pt.# XXXXX XXXXX and retails for $6.53. Bel Ray makes a sport trans oil called V Twin Sport, pt.# XXXXX $8.14, all tucker rocky part numbers and should be readilly available at most any MC retailer.
Hope this helps.