How fast is a Yamaha TTR 125?

Many factors come into play, a stock bike with any changes in gearing for instance a larger sprocket in the front or smaller in the rear will slow the rate of acceleration but will provide a faster top end speed, although it may take longer to achieve it, to the contrary smaller sprocket in the front or a larger one in the rear will decrease overall top speed and increase acceleration. Example would be like riding a mountain bike in first gear instead of tenth gear, easier to speed up but cant go as fast with all other things being equal, a bone stock ttr 125 le might hit 48mph with the wind at your back and a light rider ...just my two cents...