Sounds like the low end is lean. I'm not sure if that has a low-end needle or an air bleed, but in either case, you need to richen the low end.

You can easily tell the difference - If it has a low-end needle, the adjustment screw will be inside the ring that has the throttle arm on it. If it's an air bleed, there will be a screw (Usually just forward of the throttle arm) and a small hole in the front, or top (forward of the main throat)

If it's a needle, open it in 1/8 turn increments.

If it's an air bleed, close it in 1/8 turn increments.