[djjjr42]

Those mixture screws should just be used for fine tuning. Make sure you have the idle screw set properly. For the jets it is easy peasy to find out their sizes. Just twist brass tab off that circular piece on top, and the 4 jets are right underneath there. All you need is a flat head to pull them out. The mains (big ones) pull into 4 pieces, have emulsion tubes in the middle, fuel jet on bottom and air corrector up top. They slide into the top piece that's threaded. The idles are just 2 piece with the jet on the bottom. You should easily spot the stamped markings on each piece to see what sizes you've got. I'd recommend giving them a thorough cleaning, especially if the carb sat for a while. For the venturis you may be able to peek in through the barrels and see them stamped on the edge, but they are behind the aux venturis (where the fuel comes in). I had a lot of fun pulling mine apart when I first got it, and rebuilt it with a new gasket set (pretty cheap). Just be careful with the screws on the top plate, and remember you are working with aluminum, so don't over torque anything.

Runs like hell after 4k rpm... as in like shit or like a bat out of hell? Unless you and the guy live in the same climate and at the same altitude, you're probably going to have to change some jets to make it run right. Luckily they aren't that expensive. Venturis and emulsion tubes are a little more pricey though. Keep in mind that every engine is different so what may work for someone else may not necessarily work for you. I am using a wideband sensor and gauge, that helped me out a ton with tuning. It's hard to really tune by ear, feel, or otherwise.

What type of exhaust are you running? I use a full RB system with mine. If you're on a stock exhaust you aren't going to gain much power from that carb alone, because the stock system is really restrictive.