the max speed is the fastest it will go (heheheh) but for 125's prob near 50ish, however if your riding top speed on a dirt bike, you not riding dirt.
Stroke like 2 stroke or 4 stroke ? a 4 stroke is like a car engine, runs on straight gas, a 2 stroke fires each time, higher rpm , needs oil mixed in gas. You will need to learn something more about this if thats what your asking. better read first before buying.
