i tried the 10w40 route and my bike was a bitch to shift missed gears like a bitch. a guy told me about bel ray. tried it instint improvement. some claim that its not good since toomey dont recommend it but after field testing it, it was way better than just oil.
the atf type f fluid deal i going to try it next. belray looked like it, smelled like it, cost 4x more.
i remember after getting my truck tranny rebuild that put a semi hard shift kit in it. it had type f in it and would shift good and hard, second gear scratch, changed the fluid to regular decron whatever and didnt shift as good so i changed it back.