Just to give some people a greater insight into 2 and 4 stroke engines I have a bit of interesting info and a good comparison of a 250 4stroke and a 125 2stroke:
Link:
http://www.deepscience.com/articles/engines.html
Here's a good comparison, note the horse-power ratings, torque ratings and the RPMs:
2005 CR125---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Significant changes to the air intake boot and a new 36mm Mikuni TM-x carburetor and new cylinder porting give the engine a boost in performance to improve mid-range and over-rev power delivery. Combined with
significant weight reductions achieved on the frame, rear brakes and hub design, the power to weight ratio gives the CR125R capacity to deliver dynamic bursts of power to ensure its place at the top of its class.
Refined rider comfort and ergonomics are matched to the new frame design enhancing maneuverability and control giving a high-flying ride reflecting its works lineage and championship-dominating heritage.
* Engine Type Liquid-cooled 2-stroke single
* Engine Displacement 124.8cm3
* Bore & Stroke 54 x 54.8mm
* Compression Ratio 8.7 : 1
* Carburation 36mm Mikuni TMX flat slide (TMX01B)
> * Max. Power Output 41 bhp at 11,500 rpm
> * Max. Torque 27Nm at 11,000 rpm
* Ignition Digital electronic with 3-D mapping and electronic advance
* Starter Primary kick
2005 CRF250R------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A small bike that everybody can enjoy. Sure to become one of the mostpopular dirt bikes on the planet, the lightweight and easy-riding CRF250R provides just theright combination of performance and handling for long days of riding fun.
* Engine Type Liquid-cooled 4-stroke 4-valve SOHC single
* Engine Displacement 249.4cc
* Bore & Stroke 78 x 52.2mm
* Compression Ratio 12.9 : 1
* Carburation 37mm Keihin FCR flat slide carburettor with throttle position
> * Max. Power Output 42 bhp at 11,000 rpm
> * Max. Torque 28.5Nm at 8,000 rpm
* Ignition Computer-controlled digital capacitor discharge with electronic advance
* Starter Primary kick