KV is 1000 rpm per volt with no load. The different weight of motor gives bigger magnets and thicker stator which enables the heavier motor to turn a bigger prop.
As for losing bolts you need to invest in some blue loctite
and tighten the bolts with loctite till they are snug and not crushing the firewall.
Originally Posted by skarface
If 2 different size motors have the same KV does that mean they are the same speed?