A little background on brushless motors. 

Brushless motors are much more efficient alternatives to traditional brushed motors, primarily because it does not have a brushed commutator that induces friction and reduces electrical contact efficiency as the motor turns faster.

Brushed motors vary their speeds according to the voltage supply, thus requiring very simple speed control mechanisms made of (basically) variable resistors. Brushless motors require computer controlled speed controllers which not only varies the voltage supplied, but also alternates the electrical currents on the electromagnets within the motor, thus allowing higher and more precise speed control. That's why brushless motors usually have a kV rating, or RPMs per Volt rating. You can't find this with brushed motors.

Back to RC helicopters. 

I did an experiment with William yesterday evening. His 4100kV brushless motor with 12T pinion hit a max headspeed of well over 1700 rpm. He was hovering well at slightly below 1500 rpm. With his setup, his efficiency was only 65%.

As for my brushed setup, I had slightly less than 1300 rpm at full throttle. With the weight of my heli, it could hardly fly anywhere above knee level. 

... which brings me to discuss the optimal headspeed of the Honeybee.

My heli was pimped with upgrades that added quite a significant amount of weight. If you had the original setup, you should be hovering at a headspeed somewhere below 1000 rpm.

If you had a heavy honeybee like mine, your comfortable hovering rpm should be 1400 rpm with untrimmed blades, or 1500 rpm with trimmed blades (approx 5mm off the edges.) The higher your headspeed, the more responsive your heli will be, the shorter your flight time as well.

You would want your headspeed to hit as high as 1700 - 1800 rpm so you can have adequate "punch" when you needed it.

There's a good headspeed calculator tool here:
http://www.runryder.com/helicopter/gallery/32055/hdspeed.html 

Here's what you should key in to get your calculations as near to real life as possible.

Lipo Cells: 2S
Lipo Volts: 3.7 (2s = 7.4v)
Efficiency: 75%
Gear Size: 140T

These are some of my findings for different rating motors against pinions.

3100kV 14T - Esky has a cheap outrunner for this, but I cant' find suitable pinion.
3600kV 12T - Pretty standard setup for most brushless FP honeybees.
4100kV 11T - Some people are using this for the punch!

I will drop by AceHobby tomorrow to see if I can grab a brushless motor. But first, I need banana plugs to solder onto my new ESC so I can use it on my Belt CP...