Very easy install, took about 20 min or so. There is a noticeable difference in my YZ250 after the install. Most notably in the lower RPMs. Very happy, I will be ordering another for my sons KX65.
Purchased for a Yz 250, loved the way it made the bike feel once I finally got it on there, I had to sand it down to make it fit up against my flywheel like it is supposed to and it looked nothing like the picture posted. Performance wise it is good but coming out of the box and not ready to bolt on is the reason for the rating