yz400 questions

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  • Cavi

Posted May 26, 2009 - 12:29 PM


okay, I now have brand new engine, top and bottom, finally got it running half decent, still having some jetting issues, I am at the point that I am ready to upgrade to a newer style carb, will any 450 fcr fit or do I need a specific year? I also heard that the ktm 2003 to 05 450 carb would fit right on. Right now I still have a small stutter about 3/4 throttle, while holding it constant. JD jetting told me that is normal for a WR ignition box which I am running. Is it possible to run the yz box with the WR stator? The other problems with my current carb are basically because it is worn out and it has been driving myself and m mechanic crazy. It started not wanting to idle, so we removed the hot start setup, then it would idle, and run good, but once hot it would only start with the choke pulled, and even then with great difficulty, JD jetting told me to swap the air pickup jet, from the back of the carb from a 75 to a 100, apparently the 75 was stock in the wr and the 100 in the yz. This made it run worse, so we tried the jd red needle with a 45 pilot. Now it will fire up, not easy but better and without the choke, but right off the bottom I have a small uneven jerk, making it tough in tight singletrack. I would have to go to a 48 pilot to mess more as I am 2 and a half turns out on the 45 pilot. ut every time we open the carb up we end up with problems of a wierd fuel leak from the float, it seems fine, put it back togeather, and it works fine for 5 minutes then leaks, take it apart and put it togeather again and no more leak. anyway I am tierd of this oddball old style FCR.

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