[Barnsnake]

Unfortunately, the testing depicted in your video is not very useful. The carburetor and the timing advance curve are designed to make the engine function properly under load. When revving an un-laden high performance carbureted engine you will almost always hear some blubbering or other odd behavior at some constant RPM. In some cases there may be an rpm range that the engine will not maintain without load, due to carburetor metering transitions and/or timing advances.

A detailed description of what the engine does "wrong" in on-road operation would be helpful here.