Too slick? Isn't that the idea of oil? The honda dealer probably justed wanted to sell their honda oil. I know a lot of wingers and have never heard of that condition. Did you check the wing blog?
Yes, not that Amsoil is too slick, but a full synthetic oil is not recommended in the Goldwing due to it being too slick and causing the clutch to slip. Yeah, I know, this is not a Goldwing site.