[lincpimp]

Ok, here I go...

1st lets start with motors. If you have 2 motors, that have the same exterior dimensions and weight (weight is a good way to compare similar motors) they should be able to put out similar wattage. Motors are generally measured in wattage (or horsepower, 1hp = 746 watts).

Keep in mind the internal constuction is very important. You may compare a new castle 4 pole motor with a 2pole feigo or clone (such as the vxl motor) and find them very similar, but the 4 pole motor will be more effecinet and produce more power (watts).

So you do need to know the construction of the motor and the exterior dimensions, and weight to be able to get a feel for what you will get.

Also you need to consider kv. Kv is rpm per volt, so you generally pick a battery to suit your motor (or vice versa) considering your desired speeds, the motors max rpm, and what gearing you can run.

And keep in mind that if you have 2 motors that ideantical (brand, size, weight) and different kv they will be capable of the same total output. For example you have 2 s can size 2 pole motors, one with 2000kv and the other with 4000kv. Say the max rpm is 40k rpm. So you can run a max of 10volts with the 4000kv motor, but you can run 20 volts max with the 2000kv motor. The amp draw will be half as much on the 2000kv motor compared to the 4000kv motor, by virtue of the relationship betweens amps, volts and watts.

This formula - volts x amps = watts is very useful. And by swapping values you can get watts/amps = volts and watts/volts = amps, also very useful

For example, say you have a motor that you would like to use. It can output 1hp (746 watts). Now you have kv options with this motor, lets just say you have a 2000kv and a 4000kv option. And the motor has a 50k rpm max

So with the 4000kv you can run 11.1v - 3s lipo

And with the 2000kv motor you can run 22.2v, 6s lipo

Do the math, for the 4000kv motor, 746/11.1 = 67.2 amps

And the 2000kv motor, 746/22.2 = 33.6amps

So you can see how the amp draw is cut in half by doubling the voltage and slecting a motor with half the kv rating. Most will agree the lower kv setup will draw less amps than the formula shows, as lower amp draw prouces less heat, and heat costs power and lowers effecientcy.

As far as comparing the motors you find, best to do some google searching and try to find some actual user data. Most of the no brand ebay motors are not going to be made very well, and there do not appear to be any "diamonds in the rough" so to speak.

Good luck with your research!