I posted on this and got some advice. I too have the 03' 450CRF. everybody says to grease the headset bearing and the linkage. I change the oil every three rides. Some do it every ride. I think the jetting is fine. My mechanic had an 02' CRF and had to re-jet it. He now has the 03' and thinks it's good without jetting it. Put a skid plate on it and change the plastic engine guards with some metal guards. Other than that, do not let it sit and idle to much as I have found mine overheating. Oh yeah, put a set of radiator braces on it. I had a couple a wash outs and have bent my radiator already. Could have been prevented. As far as break in, I rode my easy for about 1 hour. Then opened it up a bit more the next ride. Third ride, I rode it all out. I changed the oil every ride for the 1st three rides. Now every three rides.