[lincpimp]

Well, first off I would say you need to go up to 8s with the XL2 esc, or higher if you can find a controller to do it... Higher voltage means less amp draw for the same load.

Next, you want a motor that will turn at least 40k rpm, and preferably higher, like 60k. So you will need to go to a very well made (expensive) motor such as a Neu or whatever else is out there that is made well and balanced (4 poles design). A better motor will be more efficient and the higher rpm will allow for shallower gearing, and that will lower your amp load throughout the speed range. Your 900kv motor died due to overgearing... If you had put 12s through it may have survived (half the amp load) and your pinion could have been half the size thus startup load would be greatly reduced. You could probably do this with a Neu 1527 with kv around 1800kv on 8s will give around 50k rpm max and should have enough torque and mass to endure what you are throwing at it....

It would be nice to know what the horsepower (wattage) requirement would be to get to speed, and then to maintain speed. A that point it would be easy to determine the voltage needed with the amp capability of the battery and motor and esc that are available.

But I know that higher voltage and more motor rpm range, and thus lower gearing is the way to go.