A 2 stroke MX bike will have a much higher acceleration rate than a 4stroke china bike or any 4stroke under 140cc (non motocross). It may not have a faster top speed with the stock gearing as MX bikes are designed for close circuit tracks and bottom end power is essential to provide snappy acceleration to keep ahead of the pack. But if you put a smaller sprocket on the rear or a larger on the front a KX65 would blitz a 120cc 4stroke. With all this in mind please understand that a motocross bike going full throttle in 6th gear on a straight will potentially blow the engine up as MX bikes are made for an ‘on and off the throttle’ riding style. It is for this reason that 4stroke machines are commonly found on the road as opposed to two strokes. So in summation, if you want a race bike that is loud, aggressive and has a high top end with raging power-band then a 2stroke 65cc MX bike is the go. If you want predictable, tangible and linear power that can sustain flat out riding in top gear for a prolonged period of time then a 4stroke is the way to go.