Recently picked up at ST270 the other day for doing my sidewalks(use a tractor or atv for the rest of the driveway). Model #932001 Serial #013679.It starts and runs very easily even if it is cold but I'm having and issue with the throttle and choke. I can move the choke left or right from the center setting but it starts to die off after a little bit. The throttle lever on top makes barely any difference in RPM, seems to just be full throttle all the time. I see there are two adjustment screws on the side of the carb but I'm not sure which screw does what and how to properly adjust them. Any suggestions would be great.