Differences in WR450F Among Years

Where, if at all, can I find a compilation of all the changes made to the WR450F since 2003 until present? I'm only concerned with changes regarding the engine.

Not sure what you're looking for exactly, but on a basic level, there are two different WR450 engines. Gen1 was '03 to '06 in the steel framed bikes. Gen2 was the '07 to '11 (and, it would appear, '12) aluminum framed models.

The Gen1 engines were dry sump with and external oil tank built into the frame. Top engine oiling was done by means of an external oil manifold. The cylinder tilted forward at about 10 degrees.

Gen2 engines are also dry sump, but the feed oil reservoir was integrated into the front of the crankcase casting, and the external oil lines for feed and return were eliminated. The top oiling passages were integrated into the crankcase, cylinder, and head, eliminating the external manifold. The transmission, while it retained the same ratios, was widened by about 12mm for strength, and the cylinder stands straight up.

There is relatively little that will interchange between these two designs. The complete clutch shares a number of parts, and is basically identical through the whole range, but there were some minor changes made in later years. Pistons are also interchangeable. Other than that, not so much.

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