Most likely the low end mixture is a tad lean. Check the manual on the engine and increase the low end mixture a bit. Usually, there is a small screw adjustment, sometimes inside the idle bar on the opposite side of the throttle, and when you make the adjustments, do it in very small increments, like 1/8 turns. Remember, righty-tighty, lefty-loosey. So, turn it out or counter-cloickwise in 1/8 turns to richen it up a bit.

CGr.