I have no idea what the 0-60 time of a KDX would be, but I could make a guess. I know that a Street Legal DRZ400S, which weighs almost 300lbs, has about 37 hp but good torque, and 15/44 gearing (top speed 103 mph) and COMPLETLY stock runs a 0-60 time of 5.5 seconds. Not too shabby. A slightly modded KDX should run alittle less. Maybe 5 seconds?
I have had my DRZ400 (dirt version) which is way modded, 0-60 timed with a special radar thingy. With 44 hp and 28 lb-ft of torque, 14/47 gearing (max speed around 85mph!), and weighing around 270+ my fat ass=500, I got 4.6 seconds, with a street tire out back. That is pretty damn fast, IMO. :p