Don't give up on it, it is a wonderful engine.

Make sure that you have no fuel system issues and that there is nothing obstructing the pressure nipple.

Check the entire fuel system to be sure that you do not have undo restrictions on it.

e.g. with the tank bone dry, hook up a clean tube to the pressure tube, using a short piece of brass pipe... disconnect the fuel line at the high speed needle. BLOW into the pressure tube side, air should FREELY exit the carb side.

Note that overly long lines will cause increased pressure ( or require more vacuum on the carb ) which fouls up the carb settings.

Once done, set the engine needles to their defaults and start over tuning.

The low and high end should start out rich.

Lean out the high end with the engine at full throttle, until it starts to speed up, out of 4 stroke range.

Bring it to idle and check the idle.

Try to get the engine to idle consistently without slowing down over time.

Once you have this, richen it up an additional 1/8 turn but no more.

Then go back to the HS and adjust for highest RPM's then back off from that about 1/8 to 1/4 turn.

Finally double check transition and do pinch tests.

The T.H. engine does not come into it's own until you have run about a gallon through it.

Prior to this you'll find it a bit touch vis-a-vis tuning...