ive got a crf230,great bike,but they are badly restricted.ive put a pro circuit exhaust on(if your using it on the road as i do you need to make a baffle,i removed the end section then machined 5 discs with hole bored in the center the same size as the exhaust spaced with 1mm washers the end plate is blank drill bolt holes and assemble.I have not found any restriction.It sounds quieter but great and its acceptable. )you then need to increase the jet size and remove the air filter snorkel.I went from a 13 tooth front sprocket to a 14. It´s a completely different bike,it goes like hell.Where i live in England we´ve got some evil lanes and enduro courses ,my bike will go anywhere.And keep up and beat the best of bikes.