i would say as a farm bike that it is in the low 80 km per hour
75 mph to 80 mph is the top speed of Yamaha ttr 250. This is true however you could increase or decrease your top speed by changing sprocket sizes, e.g A stock yamaha ttr250 with 14/44 gearing will reach approximately 140km/h or 87mph. Note i own a Yamaha TTR250 and have tested the bikes top speed.
on a basic TTR-125, the top speed should be somewhere around 45-50 MPH
55mph
a stock ttr 125 goes 52 -55
150
45 to 50mp
120 mph
My 2012 ttr 110 can go 50-55mph
50-55mph stock
45mph tops
90 km/h
i have a Yamaha ttr 125le and i got 58 but i am sure it will do 60