Eighty is getting near the top end for a 650. Wife and I had one for a while. I rode it a few times, I never toped it out but I suspect somewhere around 85 to 90. The engine would be turning a lot of RPM at that speed.
You can fairly easly change the air intake and exhaust then rejet the carbs. Adding 10 maybe 15% power. But, the RPM will be still high.
Nice looking bike, great for cruising, but in my opinion not for running at speeds over 70 MPH for long periods.
Don't confuse a 650 V Twin with a 600 cc sport bike.