Can I overvolt a Neu ?

[SpEEdyBL]

Just try using 3s first. After that I bet you won't even consider running 4s unless you are crazy or are geared too low in the first place.

[zeropointbug]

Yeah, you won't want to even run 4s anyways, it will literally fly on the 3s. No, you shouldn't really run the motor at those speeds for very long at all... besides, what controller were you going to use? The controller might not even like 67,000rpm, could overheat.