What mixture are you running now. full synthetic oils usually run 50:1 semis 32-40:1 A two stroke will smoke due to the fact that you are burning oil. If you are to rich on the fuel mix you may oil foul the plug. The screw with the spring is the idle adjustment screw, the other one is your mixture screw. Most mixture screws are stock at 1 1/2-2 turns out. I would start at 1 1/2 turns out, turn it all the way in(not hard) then turn it out 1 1/2 turns, from there turn it in and out until you find your highest idle, if you get to less than 1 or more than 2 1/2 turns out the pilot jet needs work if you are within those limits then slowly turn the screw for the best throttle response(make sure you have a good plug and gas in it when doing this) Also how many hours are on this bike. I will tell you that 2 stroke motors don't usually have a lot of torque in the bottom like a 4 stroke would you have to be in the power band for optimum performance. I would suggest getting a manual. Check the side of the engine for an oil sight glass if it doesn't have a dipstick. A small 2 stroke like that will take less than a qt. in the gearbox.