The bike is a 2004 WR450 that I purchased as an unfinished project (came in many boxes). I’ve finished building up the engine and thought I’d have a look at the carby internals to see what jet sizes it was using. I simply assumed it was a standard WR450 carby, but the model number on the side of it says 2S21 rather than the expected 5TJ1 or 5TJ2. I did a search and all that I could find was that the 2006 YZ 450F used 2S1 as a part number prefix for some parts (including the carby), so I am guessing that this carby originated from that model bike rather than a WR. Can anyone verify this for me? Fingers crossed the carby will work with the 2004 WR engine!