I recently have purchased an ’07 Sportsman 500 EFI HO in December of 2014. It has ran fine until about a couple months ago. We mainly use the atv to pull a small wagon around the farm, and just to ride around. Recently it has been acting up. After it is started, it runs perfect. After riding for a while, when it gets hot, it starts stuttering at about 4000 rpm’s. It is weird because it only does it when it is hot. When it does it, it seems like it is starving for fuel for a split second, then it catches back up, and does it again. I called the local dealer I got it from, and they told me it could possibly be bad gas. So I got some good gas and ran a whole bottle of sea foam through it, and it didn’t seem to help. I read up on some threads of similar problems and one mentioned gas boiling. So my question is, WHAT CAN I DO TO FIX IT!! I think it is super weird because it on,y does it when it is hot, and aroun 4000 rpms, and only then. When the engine is revved, it purrs like a kitten. The problem isn’t completely messing up the machine to a point that it won’t run, but it is annoying and needs to be fixed. I really use the low end power on this quad, and right now with this problem it has hardly any, but yet it still works. Any help with this weird proble, wound be highly appreciated!