Firstly I would say that it is just too rich. Leaning out the Hish speed needle (HSN) won't stop it form stalling. You need to lean out the LSN (low speed needle) slightly. You just want to get the thing so when you apply throttle it doesn't die. Turn it 1/12th turn clockwise and try it again. If it works and you get it running (assuming it has already been broken in) start tuning the HSN a little. If not turn the LSN again (you don't want to tune the LSN first toatlly just enough to allow it to pull off without stalling). Once you have acheived this and have tuned the HSN then you can move and tune you LSN for accelleration. you do this by pinching the fuel tube and checking what happens before the engine dies. you want it to run for 3-5 seconds with a slight increase in revs before it dies. more than this and its too rich, less and too lean.

On the subject of ebay
I buy a lot off ebay. Sure some things are not so good but there are also a lot of bargains.
Firstly if i buy a buggy or truck off ebay i throw the engine in a parts box and buuy another for it. Chances are you got the vehicle cheap enough to allow you to do this.
BUT lots of people that get into nitro doen't understand what they are doing and don't have the patience to learn. tehrefore there are loads of almost brand new buggies out there that are sold because the owner is having the same problems you are.
Do some searches on here. Read, read then read some more. Try this new knowledge out on you new buggy/engine then once its all safely stored buy a new engine
Thats my advice anyway.
If the flywheel turns smoothly but is hard to turn at TDC then its most probably ok