New Main Gear Binding

[Codepox]

I have two Nano CPX, one of them needed a new motor, so I decided to replace it and also change the main gear at the same time.
After replacing the main gear, I realized that the main rotor was binding for about 1/4 of a turn.
I had two brand new main gears BLH3306, so I tried both, same problem.
I tried the new main gears on my other CPX, same problem.
I put back the old main gear, no binding.
I also swapped the old main gears between the 2 CPX, no problem.
Everything is fine with the old main gears, but I get binding with both of the new ones on both helicopters.
To be sure, I even bought a third new main gear and same problem, there is binding, it feels like the new parts are not round but slightly oval.

By inspecting the new parts more closely, I realized that they are different from the old ones.
On the attached photo, the old part is on the left and the new part is on the right.
The center hole has a "D" shape:
- on the old part, the flat part of the "D" is facing between 2 spokes
- on the new part, the flat part of the "D" is facing directly a spoke
It seems like something has changed and the parts are not coming from the same mold.

Has anybody else seen the same problem?

[Codepox]

I just got off the phone with Horizon Hobby product support.
They told me that they are not aware of this problem or a production change on this part.
They don't know why the parts from the original kit look different than the part replacement part.
They are sending me two new main gear from their inventory to try.

[nickyd]

Not sure if this is still the case, but found a thread claiming gear mesh can be adjusted by rotating motor can:

https://www.helifreak.com/showthread.php?t=472357

[Codepox]

Yes, rotating the motor can to adjust the gear mesh works great.
On the old main gear, the gear mesh can be dialed in easily and is pretty uniform across the 360 degree of rotation.
But with the new main gears, the gear mesh is far from uniform and even by rotating the motor can to the loosest setting it is still binding on one side and get really loose on the the other.
Basically confirming that the new main gears are slightly oval.

[Dustin Mustangs]

Main gears for the nano have had issues with this at least as long as I have had one which is since November 2012. After a number of frustrating returns on account of this, I started taking my nano with me to the LHS to try them out before I leave. Then the clerk tapes up my rejects and hangs them back on the shelf for the next sap.

I called HH to complain about this once and they sent me 3 "verified" round ones for my troubles. Even they were a bit out of round, lol, but they were better than anything I could source so I have them hidden under my mattress incase I get robbed. Just kidding, kind of...

In my experience tho, marginally bad ones will "run-in" over time but you will have tail issues until they do.