First, get yourself a temp gun. Duratrax is about $30 online. It is te easiest way to tune an engine. 2 turns out is a starting point. Here in Alb we are at 5400ft and we start at about 11/2 turns out. We need as much CO2 as possible. Temp the engine at around 190-200, no more. temp it while there is still nearly a full tank. The engine will lean out as the level of the fuel drops. (The bottom of the tank the temp should be around 205-2120).
Secondly, Check your throttle curves as Nanuk said. What it sounds like to me is that you are putting too much throttle into stick and the bottom end is not tuned quite right. With the heli running, bump the collective quickly past half stick and bring it back just as quickly. This will get the throttle opened enough to transition the engine from idle. What it sounds like is that it will bog and you will get a lot of smoke it might even die. This means the low end is too rich. IF it dies immediately then it's too lean. Adjust accordingly. It takes a bit of practice to get it right on. Another thing you can do is while the engine is at idle pinch the fuel line. It should immediately start to lean out and rev up a bit. If it takes a few seconds then it's too rich. If it dies then it is too lean.
Once you get the bottom end close try to hover again and try to bring up the engine. If your throttle curve is too low then the engine is trying to spin blades as they try to bite more air. You want to get the engine speed up before you get pitch on to the blades. Carefull not to overspeed the engine at the bottom of the curve.
Now from the hover point where pitch and throttle curves are just right you need to get all the power out of the engine if you want to pull out. So the curve should be steeper at the top then at the bottom.
Hope this helps. It is hard to explain this through writing.