Just a thought....but you say the engine is 2 weeks old? What about the clutch? perhaps the clutch bearings are shot? Shot bearings can cause all sorts of problems....I once saw a guy try to tune an engine ALL DAY, ....I told him to stop chasing the tune and check the bearings, he didn't take my advice, 8 hours later he finally checked them and they were shot

Also, if the engine is brand new...definitly heat the case before trying to start, make sure it's at bottom dead center, and you might want to add a shim under the head to take away some compression (you can take the shim out once the engine is broken in)

Also, are you using a starter box? or are you strictly using a roto/drill?