suspicious unofficial 393 motor

We have got several 393 motor and I doubt these are unofficial motors. Evidence are following:
1, official 393 gives a CCW rotation if you asign 127 to that motor in ROBOTC, but these motors, some a CW and others are CCW.
2,motor unit inside 393 is not solidly attached to the frame.
3,screws in the frame is a little smaller than our earlier motor’s. Retailer told us that is new motor. I’v got a picture of two different motors in below.
There are many other little signs, like pins are much easier to be detached than before; torque is stronger than before…

I just wonder are these really the new motor settings or we’ve got unofficial motors.
Thanks guys!

its most likely refurbished with a little extra grease and cheap replacement screws, you should probably contact vex support to make sure it hasnt been illegaly modified or this is really a new 393 version

some pics of the inside would be nice

This looks like the labeling on Chinese sold VEX motors, they use this as a ‘legitimacy’ watermark to make sure parts were purchased through them. I can’t confirm this 100% but from what I’ve seen, this is generally the case.

the frame & wire are pretty new. I’m thinking it’s more like a self-made motor by some other factory. pics of inside.
the gears are much different in color, that is materials or thermal treatment.

indeed these motor from a chinese retailer. what do you mean? they use a different setting?

All in all, even if chinese motors are a little bit of different, at least all motors should rotate the same direction if I give them the same value. otherwise, it’s gonna be a disaster trying to figure out CCW & CW.

ok, I think I’v got some hard evidence. the model number of motors are different. this is FS130-KT…
From VEX wiki, it’s FS130-FT. Also the label and the number are in different side which cause motor rotate in different direction.

more details are coming up! To identify which is official and which is not.
It’s easy to tell, gears on the right are official, they have circles at the bottom just like annual rings. these are coming from lathe. A precision-machining technic to fabricate shaft, gear and stuff.
Gears on the left have many small “freckle-like” feature on the bottom, try to imaging smashing a mud pie onto floor and when you pick it up, it will have all these small freckles on the bottom. This is like a casting method which is way different from lathe-machining, of cause much much much cheaper.

VEX probably chop and change manufacturers from time to time perhaps resulting in minor changes to internal gears and so on. We have motors here with internal gears that are quite different looking but still the same size/pitch/ratio. Never encountered screw size changes however.

We’ve had the occasional motor that runs the other way and if you search the forum there’ll be a few posts from others mentioning this issue too. Yes it’s a pain and really it shouldn’t happen because any half decent QC process would catch this.

Find the batch number and post that too.

Perhaps try a VEX PTC test and see if it passes. There’s a document somewhere I’m sure you can locate.

I compared the motors we got last year from US, HK and official retailer in CHINA, they all have the same screws as on the right of these pics, a little bigger than those unofficial ones.
I will forward these tests to VEX official and hopefully get a result next week and post here.
I sure wish we all have a fair and joyful competition environment and resist any illegal changes. This need us all, not only follow the rules strictly, but also supervise other teams.

You say that the FS130-KT is a stronger motor? If you’re willing to do tests, it would be interesting to know the speed and torque of the motor. If it is significantly stronger than the standard 393 then this could be a real problem because teams would have an incentive to find and use the counterfeit motors.

I did a very simple test, that is directly connecting the suspicious motor with official motor, ran at full power but different direction. It turned out that suspicious motor forced official motor to rotate against its own direction and then internal gears of suspicious motor broken…

I’m interested to see what VEX says about this. I would think that it’s most likely just a different manufacturer to save some money. I’d be very surprised if this would actually be a counterfeit motor, because it doesn’t seem like it would make sense for a company to spend a decent amount of money to make all of the tooling necessary and do all of the printing and internals pretty much exactly the same, for a relatively small market. And if they are fakes, I expected they would have turned up somewhere on Alibaba, eBay, etc by now, but who knows.

Where did you get the motor from?

Chinese teams are forced to order through ‘BDSTech’, since they run all of the competitions in China, and have the ability to control the cirulation of VEX parts in china. Every single vex part has a watermark, similar to the ones you posted, such as these, example images are included. At worlds, I’ve seen slightly more detailed labels, like yours, but they contained the stall torques. Also, apparently they sell the motors that only have one ratio, and you shouldn’t actually be able to upgrade the motors, and they’d rather have you buy a new motor.

I wonder if these are the specs?
They are definitely different, but physically the same. Was the gear ratio different?

Here is one place that you can look them up:

It would be interesting to see if the thermal breaker is different, cause the K looks like it would pop earlier, but with a lot more torque for the batteries we have.
FS-130K.pdf (418 KB)
FS-130F.pdf (401 KB)

The internal gears of the “suspicious” 393 looks like the old powder formed gears while the new ones look like the new style internal gears. So it could be one they may have had in stock for over a year.

No, that’s incorrect.

I was trying to find the spec on these motors about three years ago and concluded they were probably custom made for VEX, these are the notes I have from that time, I cannot find them on the net right now.


F = Flat shape
S = Super strong magnet
1 = 13mm Armature
3 = 
0 = 

F = Precious metal brushes
T = Metal endbell
2 = diameter of magnet wire
1   21 = 0.21
1 = number of turns
0   100 = 100 turns

wire diameter is 0.21mm so areas is 0.034636mm2 or 3.4636x10-8 m2
resistivity is 1.678 x 10-8 ohm/meter
wire length = 13*3.14*100 = 4.084m

Rdc = pl/A

p = 1.678x10-8
l = 4.084
A = 3.4636x10-8
Rdc = 1.98 ohms

So the main difference between the two parts is one is -FT and the other -KT. The F and K look to mean different brush material but the windings are the same (the 21100). My guess is that they both should have the same performance wrt torque/stall current. If I can find the source of this I will post it. Note, Rdc in those notes is actually incorrect as it measures at 1.5 ohm.

Edit: OK, so K means carbon brushes. So the only difference it seems is the brush material.

Edit: typos

Great, thanks for the response. I had no way of testing against the specs, out of the country, but put up what I could find.

Thanks for clearing it up.


After reviewing the photos of these motors in detail, it does not appear that they are counterfeit, but I cannot be 100% sure with the evidence presented. These motors have been in production for over 5 years now, and over time we have made many tweaks to improve performance and manufacturing. These tweaks may account for the differences between the two motors, but I cannot tell for sure without knowing the date codes printed on the motor. Can you post photos of the date codes for both of these motors? It is printed on the “front” portion of the motor and has the form XXXXAA where each X is a number.