How fast does a ktm 520 go?

Again it depends on which model you are asking about. A 520 SX (4-speed) will top out at around 70 mph depending on the gearing. The six speed 520 EXC will run 100 mph. It's not that the 520 SX is slow its just geared for the track and there's no Motocross track that you would you run 80-100 at.