How heavy/tall are you? Factory settings on a 125 probablly are callibrated for a 155lbs rider, riding motocross, which requires much stiffer suspension thatn wood trails. If you dont go off any huge jumps and are under 200 lbs, and loosen up of the compression and reboud adjustment, but set the sag or preload height to something of your liking. A softer rear shock will cause the rear of the bike to squat under heavy acceleration and will ultimatley give you better traction, which is key in getting that mighty horsepower to the ground. Like wornknobby said, you can have all the horsepower in the world but if your spinning the tire you ain't going nowhere. Suspension calibration on any bike is probably the most important performance enhancing modification you can do to you MX'er.