sorry if this has been covered recently, this is my first time on. i was under the impression that i could order a yz450f exhaust cam and install it right into my 99 yz400f to get the benefit of the automatic decompressor. the differences are that the tooth shape on the sprocket won't let the chain sit down as far - suspect a different chain style is in the 450. the sprocket looks like it's pressed on but can't be swapped because all the decomp stuff fits with it. the lobes are narrower (no big deal) the base circle is .010" bigger, that just means a different range of shims, there's a tiny bit more lift and less dwell (the lobe is narrower and pointier) i guess that makes it a torque cam, but the timing may be different, the dots line up in a different place. any help? someone out there knows how this has been done before. i'm worried about my friends not being able to do the starting drill as we're using my bike in the supermoto team race this saturday!