I had a CL77 when I was a kid but what I wanted was an R27. I hadn't any idea of what a bear cleaning the R27's oil slinger would have been. A K75 input spline lube is a walk in the park by comparison, so I lucked out with the Honda. An R50/5 might have gas mileage in the high 40s, Firehose, but is heavier and taller than your specs.
A Suzuki TU250x or a Honda Rebel would meet your specs easily.