ORIGINAL: MinnFlyer
DO NOT run it without a prop!
With no load on it, the engine will SCREAM for about 8 seconds and then seize up - never to run again!
Dang, he beat me to it! Don't run it without a prop, not worth the risk. One pump to full throttle and it will get some scary revs. I ran some engines before with a prop and spinner on them bolted to a block of wood that was clamped into a vice.
http://www.youtube.com/watch?v=DpgAeYsw9Oc