I assume the engine comes with the installed restrictors on the adjustments. I would remove that from the high speed needle valve. The high speed needle valve is the one inthe fuel line from the tank. To richen up the engine you unscrew it, do that in very gentle steps, partial turns (or as we say clicks). The high speed needle valve has a knurled surface and a spring clip to keep it from moving when set. That is what makes the clicks. The high speed needle valve should be somewhere between 1 1/2 to 2 full turns out. Two turns being rich, 1 1/2 being lean.

Tune the engine by ear for max RPM, then move the high speed needle valve out a few clicks to richen it. Once you get this down right, the next step is to tune the low speed adjustment. It is found inside the throttle arm on the opposite side of the carb from the fuel line coming in. It is buried down in there, usually slotted so that a small screw driver is needed to adjust it. When adjusting this do it in small steps, no more that a 1/8 of a turn at a time.. An 1/8th of a turn inward leans the engine at idle, an 1/8 of a turn outward richens the idle.

With the high speed adjusted, slow the engine to idle, if it does not idle at all, then it is to lean. If it idles okay and the engine stubbles when acccelerating, it is to rich. Adjust with the engine stopped for safety's sake. Once an adjustment is made to the low speed, start engine and test again to see if it idles correctly and accelerates smoothly. If it does that, it is near perfect.

Cheers,

Chip