Fantastic motorcycle.
I had one for about 2 years and sold it about 3 years ago because I also have a much later BMW 650 single.
Aprilia made the 650 singles for BMW until about 2010. Part of the deal gave them a cousin bike to the original 650 Rotax-motored BMW Funduro. The Aprilia version was the Pegaso. It had a 5-valve head and hotter tuning than the BMW. The bodywork was also sleeker. Sumbich ran like a much bigger bike.
The Pegaso is a 650 single with dual carbs and dual exhaust headers that carry through to true dual mufflers.
Again, mine ran like a raped ape. I used both on-road and off-road. The suspension was better than the 650 BMW GS models that I rode.
The Pegaso had a few small glitches. Some folks had trouble dialing in the carbs. Mine were spot-on. Also, the voltage regulator was under the seat and would overheat for lack of cooling air. Some people relocated them to an open location. I left mine under the seat but installed a small 12V IC cooling fan on top of mine. Never gave me trouble.
One of the nicest, best performing bikes I've owned.
Alas, it is 17 years old now. Engine parts can often be had but, if you ever drop it, getting new plastic may be very difficult.
If you are looking at 650 singles, the current iteration of the BMW 650 is a fantastic and much more modern big single. Power and smoothness is a world ahead of the Asian KLR's and DR's.
My Pegaso3-