the big bore is a cyinder upgrade to 185cc u can remove to plates in the exhust at the elbow´ higher the carb needle to get richer mixture change valves from steel to carbon and down size front sprocket by one tooth the valves u need or of a dtr 125 top speed 100+´ better acceration too´ let us no how u get on ´i 2 have a 2004 in black best looking 125 by far