why are my temps so high???

[BrianG]

It's already been said, but I too think that 6s on that motor is fine as long as it is geared appropriately. It's maybe a tad higher voltage than I'd go for general use though. Gear down to shoot for 40mph max speed and it should be fine.

The reason why you don't notice a difference in speed between 12T and 18T is because on 12T there is very little voltage drop. On 18T, the increase in load (and therefore current) is causing the battery voltage to drop. Since motor rpm is a function of kv and voltage, if voltage drops, so does top rpm.