I have searched for this to no avail. Predator comes lean.. I know this. so some experience surging that may go away with half choke on. I want to get jets to straigten this issue out. I bought a bsp for my Thunderbird. and a 140 emulsion tube kit comes with a 36 main jet and 37 main jet. I'm probably gonna run the 37 on my bsp w/header and K&N air filter. I might try that 36 main on the Predator 212. any jetting tips I'm in massachusetts so were talking mabye -12F to 32F deg.