can always change the gearing iv been told by some woman who works at hein gericke who has a Rieju RS2 125 with the YBR air cooled engine but with a bigger carb that it can do a good 80 in the summer and abit more in the colder air temperatures but that does have fairings but comes to show how much better top speed gearing is im tempted to change the front sprocket on my marathon pro to a YZf R125 15 tooth to get abit more topspeed iv seen my bike on youtube when at full power doing 130kmh or 80mph