Trial and error. Mostly error. One of the biggest PIA’s going that is. You can either flood it or have it die when you yank the throttle. If it doesn’t do either, leave it alone! I’ve go an MP3 somewhere of mine dying on a high speed run as the fuel just couldn’t keep up. Must dig it out, it’s a cracker.
Anyhow, good luck, you’ll need lots of that.