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.
Orange????
Not too fast
Not as fast as a GSX-R1000
A ktm 65sx will go about 43 but with fmf pipes it will go close to 50
108.5mph
It can go 60 mph.
130mph
About 123.7 mph
70 stock
First disconnect your kill switch, if that is not it, check your plug cap, then if that is not it go on to your stator.
Very Slow! KTM's are NOT worth the money AT ALL!!
70 stock