Be aware that where we ride in the Rockies, many trails are being limited to 50 inches, with entrances actually blocked by narrow posts, gates, and large rock and gravel piles. I doubt you will want to get caught on these trails.60 inch Sport model
If it doesn't gear up all the way I will make that improvement probably with JBS machined parts. A slightly lower gear and a higher top gear may be a necessary improvement. I need a 50 mph cruise in the large wide sand washes and on some fast truck trail. I just hate to run at red line in the over rev area. The Teryx rev limiter is 7,800 rpm and it hits the rev limiter in low range. In high range the speed sensor cuts the injection at about 50 mph at near 6,300 rpm. I could live with something like that but really want a 60 mph top speed. I will install a tach and a belt temp sensor to make sure the belt temp stays below 180 degrees. At 200 the belt wears faster and 260 degrees the glue melts.
I don't think it's durable because it's a single cylinder, but rather in spite of.
Single cylinder requires the use of large counterbalancing weights to keep from shaking itself to death.
Single cylinder lead to vibration. Vibration leads to metal fatigue, metal fatigue leads to, well, metal fatigue.
That said, I sure did love my XR 650...