Hi Jevi First of all I wouldn't go by what the speedo is saying if that is what he is indicating to reference speed, my lexmoto speedo showing 75 when I'm doing 60, not bad if it was 75 but is not, ask him if it feels like the bike is accelerating but maybe just not showing? For choke I start mine up and I can manage only about 30-60 sec on choke then I have to fully open other wise bike will die, just adjust your idle screw a bit on carb and see if this will improve, could be just jets and carb need good cleaning, not a hard job, check your throttle cable going to carb, does your model have EGR valve? Link to near the same carb, will show you some basics and what is responsible for what http://www.ccwthariders.com/uploads/9/7/7/9/9779070/pz_carb_tuning_manual.pdf ...ish. how could you measure speed with out access to a speed gun? I'm curious to know if I'm doing the speeds my bike says I'm doing