Unless it was my imagination, when I first changed to synthetic oil in my 02 VTX, 50,000 miles ago, I immediately noticed that the "clunking" sound/feeling when shifting, was gone. The shifting became smoother. I always use Amsoil synthetic motorcycle oil.
03 1800R (purchased in Texas in 2013 with 20,000 miles), Spiegler brake/clutch line kit, custom paint job by BD's Cycles from North Carolina, Mussy 2 into 2 exhaust, PCIII, Hypercharger Pro, Ultimate Lowrider seats, Edge extra large saddlebags, Clearview +4" windshield, Aeromach 6" risers, Uniq Cycle Sounds speakers, lots of Kuryakyn chrome, NC Paladin engine guard, etc. "Always Expect the Unexpected"