The top speed of a stock Honda CBR 250R can vary depending on various factors such as rider weight, riding conditions, and aerodynamics. However, the Honda CBR 250R is known to have a top speed of around 85-90 mph (137-145 km/h). It's worth noting that reaching the top speed may require a long straight stretch of road and favorable conditions. It's important to prioritize safety and abide by local speed limits and traffic regulations while riding.