The jetting calculator works better on the 790 engines than the 865 engines. I've found that while a 790 engine with free flowing pipes and pod filters can take a 150 main jet or maybe even larger, the 865 engines probably can't go much bigger than 140. That's just my personal experience. Maybe others have found a way to go bigger, but the 865 cam seems to be the limiting factor. I'm running relatively open pipes and pod filters on my 865, but really need to replace the cam to get any more horses on the top end. That's going to be my next project.
