need help with converting a hyper 7

[BrianG]

Yeah, I too would be looking in the 2000-2600kv range for 4s. Otherwise, you're gonna have a heck of a time gearing it down enough and/or use really small tires (smaller tires is like gearing down) to keep temps down.

The CC2650 motor (essentially a 1512/2.5d) would also be decent on 4s, geared around 46/14 would give you around 40-45mph speeds.