Sounds like you are just not getting enough fuel to the engine. Is the tank up close to the firewall, and roughly centered on the carb? Are you sure the hose is not pinched somewhere? Unless you have a restriction there's no reason the engine wouldn't pull rpm. Provided the HS needle is open far enough.
I also see this at least contributing to the problem:
ORIGINAL: outacontrol41
...new... ...in the process of breaking in the engine
Until you have the engine pretty well run in you have to leave the LS needle fairly rich, if you have it turned in too far the engine will go lean about 1/2 way open on the throttle.
Your best thing will be to pull it out and bench run it for at least a half hour or so, then with the needles more properly adjusted you can finish the job on the plane.
If you just have to do it in frame, open the HS needle about five turns and see if it will run up to speed, then you can start leaning it out.
Bill.