2004 XB12 jumping out of 4th in between 4-3,

[Buelleybane]

Hey I'm new to the forum and I've kinda jumped into the Buell's with both feet. I bought an 04 XB12 that apparently had a shifting problem, it's jumping in between 4th & 3rd under acceleration. I also just traded one of my quads for a 2002 S3 that is a true barnfind. It's only got 7800 miles and has the fork seals leaking. I've worked on quads and vehicles all my life and was just looking for some pointers and info. Thanks for any help