All of the motors building the Epic based motors all get them from the same place so it all comes down to 2 things that seperate one tuner from the next. They are.....
1. Integrity. There are ways to cheat at anything and motor building is no exception. You can cheat by inflating your dyno results and you can cheat by advancing the timing - or both. Most motor builders are using the Fantom Facts Machine which is good since they are fairly consistent from one to the next but there are ways to artificially inflate the numbers on them. Also, it is easy to advance the timing and get higher power numbers - especially RPM. There's more ways to cheat but those are 2 ways.
2. Attention to detail in the building process. High volume will very likely means the motors are assembled, stuck on a dyno, get the sticker and slapped in a package and up for sale someplace. Sometimes you get a good one and sometimes you get a dud. A good tuner will do all of the following (not just say they do) check/zap magnets, PROPERLY align brush hoods, PROPERLY shim the armature to center of magnetic field AND shim to remove end play, cut the comm with a diamond bit (I use a marker prior to cutting to ensure the comm is round - Hint: look for a little marker line at the base of the comm), fully seat the bushings/bearings and ensure no binding and finally take the time to break in/seat the brushes.
How do you know who does this and who doesn't? Check end play - if the armature moves in more that .010" then there is too much slop. That will equal inconsistent performance since the armature can move in and out and the brushes won't seat in a consistent spot. Be sure the comm was cut with a diamond bit and is round - hard to check without a comm lathe but at least look at the finish on the comm - it should be very smooth and no filings in the slots. Look for neat soldering on the brushes. Look at the brushes after a while and see if they are centered on the comm (brush hood alignment). There are probably a few other things but this is a good start.
Honestly, anybody can build a fast motor with the right tools, experience, patience and attention to detail - it's whether they take the time to do so or not that makes the difference.
As far as power ratings on a stock moter... I would want to see at least 66 watts, at least 100 torque and RPM in the 20K range. Generally higher RPM motors have a little less torque and and higher torque motors have a little less RPM. For example one motor might be 19,500 RPM and 106 torque and another motor might be 21,000 RPM and 101 torque. I don't personally worry about effeciency.
I haven't seen any quality issues with the motors coming from Trinity, BTW. In fact I am seeing very consistent results on the motors I am building. I get a dud once in a while like anybody else but that's just how it goes.
Sorry for the long winded post - I hope it was helpful.
