RE: feul tank mounting?
I suggest solving the problem in a step by step fashion.
Firstly, try to fit the tank (the middle of the tank) accordingly with the spray bar.
If this is not solving the problem, then reset the idle needle valve and the HSNV, do not try to get the most of the engine, and just make it run rich. If you still have the problem (the engine dies when there is only 1/3 of fuel left in the tank) then, your engine is overheating because of a number of reasons (Cowling, old engine, bad fuel, still bad tuning etc.)