I figured with a name like easy rider you just naturally rode a harley...LOL
I did run 20W50 Valvoline full synthetic in the Harley, but it had an upper end knock when hot, so switched to dino 20W50 and much less upper noise, other HD riders were reporting same results, AND you are right the motor
and trans ARE separate and I DO run Mobil1 full syn gear oil in the trans.
I think that no matter WHAT you run as long as it doesnt have a big circle on it and say "energy conserving" on the bottle you could probably run anything safely (10 40 or heavier) IF you change oil every 2-3000 miles, now will a full syn vs a semi syn vs a dino matter if they're all JASO m2 certified and are changed regularly? Probably not. So, to each his own. I'll report back after I've put a few hundred on the T4 change