Cyclic gives good advice.

If you want to look farther, take the carb out of the crankcase and look back up through the venturi from the bottom. There is a cat-eye looking slit in the spray bar. This slit should be looking directly at you when you look up into the venturi. Also you can see the end of the low speed needle? It should be half way accross the slit when the throttle is held wide open.

If you get it running with the high speed and low speed set correctly, if you still cannot get the mid range to not be rich-- as a last resort, loosen and twist the spraybar a slight amount one way or the other and see what the mid range is like. Make sure that you have marked the center position of the spraybar before you move it though.

Be careful to not create any air leaks or your troubles will just begin.

Good luck,

Jim