I'm nor aware of a bulletin about jetting for the KLX250. I'm running two sizes down on the main jet on my DR650 that is stock except for a stage one camshaft. With stock jetting here it had a bad stumble coming off full throttle that would near send you ever the handlebars. LOL! Been running the two sizes down for several years now. It runs nicely at the high elevations. I would go back to stock if I rode below 4,000'.