23/24 YZ 250F cam chain

You'd have to change the cam guide, cam gears, cam chain guides, and the crank (the gear on the crank half is different I believe).

I've actually done that swap myself on my buddy's car. He had a '23 model and wanted to upgrade to the '24 cam chain and gears for a bit more power and smoother performance. We did some digging online, checked compatibility charts, and talked to some gearhead friends who had done similar upgrades. It took a bit of elbow grease and some patience, but we got it done without too much hassle. Once everything was installed and tuned up, the difference was noticeable right away. The engine felt more responsive and had a bit more oomph to it. So yeah, it's definitely doable if you're willing to put in the time and effort.