I'm having an issue with my idle adjustment on my 426, I currently have the idle adjusted all the way high (screwed all the way in) but it still won't idle. The jetting is as follows, 160 MJ, 40 PJ, JD (red) 4th position. The fuel screw is ~1.5 turns out. I did some modifications over the weekend that included swapping out the ZipTy fuel screw with the stock one, replaced the accelerator pump diaphragm. The bike runs well (above idle) everywhere else, the plug looks good and everything (slide etc.) else on the carb looks good. Could it be a vacuum leak? Should I start with the fuel screw by adjusting it in and out? Any input is appreciated.