The RC valve on a Honda is like an exhaust valve on a snowmobile or other two stroke engine. So it should change the hight of the exhaust port making the engine preform better at all RPMS.
I can't tell you much about whether '01 was the last good one or not, the '08 I PDIed this past summer seem to work good for me, not like my 250 tho, but it was comparable to the '01 CR 125 we took on trade.
'03 YZ 250
Tag bar clamps, titanium 200 foot pegs, Rental American Addition bars, RG3 suspenion, Hotwheels graphics, Griper seat cover, and Carlsbad tires.
