What happens after some prolonged above-average stress is placed on an electric motor? Something has to give – in this case, the internal nylon gears. The following instructions walk you through an e-bike motor gear replacement, specially how to replace the nylon gears in a Bafang 500W G360 rear hub motor.
After breaking two spokes on the rear hub of my Specialized Roll Sport and Bafang e-bike conversion, my motor stopped working. The bike wouldn’t operate, and it made weird grinding noises that indicated a serious issue. I believe the difference in the radial forces from the spokes being broken caused the motors gears to shear off. I did not know the root cause at first, but the bike would not move and there was a funny “whirring” noise that occurred as the throttle was pressed and the motor spun.
Opening the motor up, it was abundantly clear what the problem was. The nylon gears had effectively turned into marshmallows and were flung around the entire motor. I regularly over extend my hub motor, but am happy with its durability and response, even after two gear replacements. I hope these instructions help anyone who has had the same issue walk through the steps for successful e-bike motor gear replacement.
Step 1 – Remove Disc Brake
Using a 4 mm hex key, remove the 6 screws securing the disc brake in place.
Step 2 – Remove 3 Torx Screws
Using a T30 torx key, remove the 3 torx screws securing the face plate of the motor.
Step 3 – Remove Cover Plate Torx Screws
Using a T20 torx key, remove the 6 torx screws on the outer rim of the face plate.
Step 4 - Remove Motor Cover Plate
Carefully using a razor blade, place the edge of the blade between the face plate and the motor rocking it gently up and down to loosen the face plate.
Use a flathead screwdriver to gently expand the gap created between the face plate and motor. The easiest way is to place the screwdriver into the gap created from the razor blade and gently twist.
Tip: use two flat head screw drivers, one on each side to help gently and evenly pry the face plate off the motor once loosened.
Step 5 – Replace 3 Screws in Motor Gear Housing
Using the T30 torx key, replace the 3 torx screws that were removed earlier from the face plate. This keeps the contents of the gear housing in place. It might be useful to remove the top plate ring and take a picture. This component is made of multiple, smaller pieces. Use appropriate care when handling these parts to save you any frustration later. We definitely learned the hard way!
Step 6 – Remove e-Bike Motor Gear Housing
Gently remove the gear housing while keeping it level.
Step 7 – Remove Plate/Stem
Using a Phillips head screwdriver, remove the 3 screws holding the plate in place.
Use tongue & groove pliers to remove the plate.
Step 8 – Remove Nylon Gears
The gears are fitted tightly, so use a small flathead screwdriver to gently loosen one gear at a time.
Step 9 – Clean the Housing and Remove Excess Debris
Use a rag and any kind of precision tool to clean ALL debris and grease from the gear housing.
Step 10 – Gear Replacement
Center the bearing washer over the individual gear post, then place the nylon gears on top. Remember, that the teeth of the gears should align with the drive stem. Ensure that the gears fit properly.
Step 11 – Grease the Gears
Generously apply Mobile 28 grease to each gear ensuring the gear and teeth are completely coated.
Step 12 – Install Plate/Stem
Place the plate/stem over the nylon gears ensuring the holes on the plate align properly over the gear posts and screw holes.
Tip: Ensure that the flat side of the stem is aligned with the opposing stem on the opposite side of the motor. This is required for wheel/hub installation.
Use a Phillips head screwdriver to replace the 3 screws holding the plate in place.
Step 13 – Install Motor Gear Housing
Place the gear housing onto the stem. Make sure that the gear teeth are aligned.
Tip: Use a wrench or hammer to gently tap the housing into place. Expect to use some applied pressure to get the gear housing placed.
Tip: Avoid the gear teeth overlaying on top of each other. They should align properly.
Step 14 – Remove 3 Torx Screws
Using the T30 torx key, remove the 3 torx screws holding the gear housing together.
Step 15 – Replace Cover Plate. Align Holes and Install 3 Torx Screws
Replace the motor cover plate ensuring that the holes on the plate and the gear housing align properly.
Tip: Use an appropriately sized diameter torx key, screwdriver or hex key to keep the screw holes aligned.
Using the T30 torx key, replace the 3 torx screws on the cover plate.
Step 16 – Coat and Install Cover Plate Torx Screws
Apply semi-permanent threadlock to each of the 6 torx screws.
Re-install each of the 6 screws using the T20 torx key.
Tip: Install screws in a star-like pattern to ensure balance and avoid cross-threading any of the screws.
Step 17 – Install Disc Brake
Using the 4mm hex key, re-install the 6 screws holding the disc brake in place.
You have now completed an e-bike motor gear replacement to place the bike back in service, at least until the next gear replacement.
