Hard to say without seeing it. Lets start by saying to remove the plastic to expose the needles. Hopefully you will have 2, a high and a low. If not get a new carb. What is the range you speak of. Are you saying the throttle arm motion? When you set up the throttle pushrod you do it like a glow motor with end points etc. Now for adjusting, I start with the high and go to max RPM then back off slightly. Adjust the low next by leaning until the RPM's max again then back off a tad. You will need to adjust the idle end point as you do this otherwise the RPM will be too high to notice small RPM changes. Check the transition and adjust from there. Some will say to go back to the high and recheck. I will fly the plane and see what it does and adjust from there if needed. Remember that only very slight adjustments are needed. Slight meaning maybe 1/16 or even 1/32 at a time. Once set you will rarely if ever touch it again. Also remove the idle screw from the cover. Not needed.