I’m not sure why they made this primary reduction gear on the BBSHD out of plastic. People keep telling me that it makes the drive unit nice and quiet. If I wanted a quiet motor I’d put it under my pillow at night, or spring for a decent Sine wave controller. People say that it works like a fuse to make sure that if there is too much power going through the motor that it destroys the plastic gear instead of the expensive motor. To that I say hogwash, I ran 3250 Watts through the motor under extremely high load and the windings were just fine. The reason that Bafang uses a plastic gear as the primary reduction in the BBSHD is due to one thing and one thing only.

To save a few Yuan.

Don’t believe me? I’ve been to China and I can attest that one of the biggest complaints that the Chinese people have against their own Chinese products is that they are cheaply made. Don’t get me wrong, the BBSHD is the most reliable mid drive I’ve ever touched by a long shot. The weak point of both the BBS02 and the BBSHD is the nylon gear.

There are two things I’m super excited about with the BBSHD that are drastic improvements over the BBS02.

The first is the new white lithium grease they are using on the primary reduction system. The old lithium grease on the BBS02 was the consistency of whipped cream and it was quickly flung off the primary reduction gear which spins stupid fast, over 2000 RPM. The new grease is the consistency of extremely sticky toothpaste and it seems to stick to everything. Even after 3 months of hard riding on my BBSHD there was still grease in between the valleys of the gear teeth on the nylon gear and the motor shaft. Although these grease seems to collect on the bottom of the gear, there was plenty of it to be found on the gears itself.

The second improvement was that there was absolutely NO seepage of black moly grease from the secondary reduction system into the primary reduction system even after 4 months of hard abuse. This was a huge problem with the BBS02 and I believe it was the primary cause of Nylon gear failure on the BBS02.

Replacing the Nylon gear on the BBS02 is much easier than replacing one on the BBSHD. The biggest difference is that the rotor tends to stick with the main drive case and the press fit bearing when to stator is removed. This means you have to overcome the pull of the magnets in order to remove the motor which is pretty hard to do without damaging anything.

Remove the drive unit from the bike. Remove the controller and carefully remove the silicone around the 3 phase wires and the hall wire plug that goes into the case. Do not cut the wires or damage the insulation. This is incredibly easy to do and if you do damage the wire insulation then you will need to cover it with heat shrink tubing after you put the motor back together so the phase wires do not short against the case. Remove the 4 hex bolts on the motor side and carefully pry it apart. Pry both sides evenly. Once you get it started make sure that the cardboard gasket does not rip. Using the screw driver with the case open less than 1cm carefully go around the outside. It is important that you don’t rip this gasket and if you do that you replace it or seal the seam with silicone when you put it back together. Eventually you should be able to get the stator (motor case) apart which will probably leave the rotor attached to the BBSHD housing. If you grab the rotor with your hand and pull it really hard straight out you should get it to come out. If you have to lever it with screwdrivers then make sure to lever on both sides with equal pressure at the same time. Now you have access to the cover plate with the Phillips screws from hell. You will need to work hard to not strip these babies. Make sure to use the right size Philips head and then attach vicegrips to your screw driver. You will need to put the BBSHD on cardboard and lean on it with ALL YOUR WEIGHT and carefully turn the screws. If you’re lucky they will come out without stripping, if you’re not lucky then it’s EZ-out time. Removing stripped screws is a royal PITA, so my advice is don’t go there. Use 3 of the 4 small hex screws from the motor mounting to carefully screw into the empty holes next to the removed Phillips screw holes. This is a press fit bearing and you will NOT be able to get that plate out properly unless you carefully tighten each bolt in sequence until the top plate pops off. Remove the locking ring. This is more of a pain in the ass than you think it should be. If you have a decent pair of lockring plyers then it makes the job doable. If you don’t well good luck to you. Use a L shaped hex wrench to get under the nylon gear and pull it straight up. You’ll have to pull very hard. If your fingers slip on the wrench then use a pair of vicegrips to hold it and pull straight up. Clean out all the plastic debris and grease that you can in the hole. If you leave any plastic pieces in there it will mess up the next gear you use. I only say that because the first time I did this on a BBS02 that is exactly what I did. If I can do it then you can too. Grease the crap out of the gear with a heavy Lithium grease or Mobilgrease 28 which all I use. Do not use a black moly grease on this gear or it will weaken and fail. Replace the gear, put the lockring, replace the plate, tighten down the Phillips screws as hard as you can without stripping them. Carefully replace the rotor and the gasket. If the gasket ripped get a new one or seal the edges with silicone. Replace the stator then pull the phase wires back through the housing toward the controller. Check the insulation on the phase wires and put heat shrink tubing on it if it has ripped. Silicone the holes with the phase wires and plug-in the hall sensor plug to the motor and silicone around that as well and replace the controller.

Replacing the Nylon gear takes about an hour or so for a BBSHD vet. It might take up to 2 hours for an amateur. You will know if the primary gear has failed if the motor turns but offers little or no resistance. When the nylon gear peanut butters, it also generally becomes extremely hard to roll the bike backwards. If you think it might be the pinion gear your can pull off the secondary cover and check that first before you rip the drive apart. That only takes 5 minutes and even if the pinion gear is fine you can grease it up with Black moly grease or Mobilgrease 28.

Although these steps seem pretty intimidating I can assure you that they are not that hard to do. You can get a replacement nylon gear stateside from Lunacycle.com for $20 here. I have bought these for the BBS02 from China and they were a few dollars cheaper but they cost a lot to ship and took forever to arrive. Be aware that the nylon gears for the BBS02 and the BBSHD are completely different and not interchangeable no matter how hard you push them on.

Ride On.