Yep , they are very fuel tempermental. When you got it right its real nice but when its slightly off its a pain in the ass. Only thing i can tell you is keep your eyes on those plugs and if they get oiled i would back off that main a little and if its the right color i would try diferant needles. Hate to say it but keihin pwks after you get it ported would be the ticket. You know if you port that top end you will have to start all over with jetting, lol. I been threw the same issues your going threw with the first motor in mine and now the second motor. I know i need to back off my main this summer because in the winter it ran awsome which tells me i was to rich last summer which i suspected. The first motor i had in mine i was haveing issues and was running aftermarket CDI, so threw advise i dumped the aftermarket stuff just to rule out ignition problems so now i know if it stumbles or runs weird its jetting almost certainly. You will figure it out but i kind of think its in your carbs/jetting but I will tell you a funky CDI will act just like jetting trouble. Like i said i could be way more helpful if you were running keihin carbs. I never ran stock carbs and never will only for the simplicity of keihin carbs. A banshee is a never ending money pit, damn near as bad as a boat but damn if it aint fun to ride when you get it dialed in.
