I own two 07 TTR230's and an 07 WFR450, and have changed the front sprockets from a 13 to a 14 on the 230's, and from a 13 to a 15 on the 450, (I tried 12, 13, 14, 15 & 16T spockets on the 450, and a 12, 13, 14 & 15T sprockets on the 230, with the best results as a 14T on the 230 and a 15T front sprocket on the 450). The rear sprockets are still the standard tooth count. The Xhaust spark arrestors were removed from all of the bikes, (a hacksaw being necessary on the 230's ) ... and ... these bikes have been literally transformed! The next step(s) are to remove all the airbox trumpets under the seat, along with the "fly screens" and a re-jet. I wondered if anyone had any ideas on jetting sizes for both the 230 and 450? also; How great, (or not?) is the 07 TTR 230 head? Would it benefit from a lil' porting, (or just mild polishing), (I've heard that they desperatly require removal of "dingleberries"), and/or an inlet valve size increase? also; The local agent also suggested removing one of the head gaskets? ... Is there more than one head gasket? and; Are there any better cams and/or pistons available for the 230's? Finally :blah: ... What is so great about all these aftermarket headers / pipes? and which one/s actually work? ... as against just making the bike sound faster by being louder!