BBS02 Clutch replacement

[Sebz]

How to replace the internal clutch (or freewheel) on the BBS02 motor.

First you will need tools and parts

1) Snap Ring Pliers (opens 20mm or more)
2) Bafang toolor cali-bike tool for internal axle lock nuts and a plier or wrench
3) Hex keys
4) Flat head (small and large) and Philips head screw drivers (small and large). You can also use an impact for the large screws.
5) Replacement clutch
6) Optional but recommended: MobilGrease28

Lets start!

Remove the rubber seal on the axle:








Now we remove the 2 lock nuts in the axle, on the drive side use a wrench to stop the shaft from spinning and insert the locknut tool and remove both.








Remove the thrust bearings and race and you end up with all this in this order (not shown the rubber seal)









Remove the plastic cover with the Philips head:








This is what you now have.... Yeah I cheated I cleaned it for the photos, you can do it too if you like and repack it with grease later! I will do a tutorial on removing the rest of the parts for a complete cleaning and greasing job!

[Sebz]

Ok now put your hand on the gear and flip the motor to slide the axle and gear out, You will end up with this and another thrust bearing in it, remove it and don't lose it!



Remove the snap ring:



Next remove the plastic ring (it's actually the ring that holds the magnets for the pedal assist system "PAS")



Remove all 5 bolts, they can be tight so a small impact drive can help.

once all screws removed you will have to insert 2 bolts in the small holes, with your hands till it reaches the bottom, I used the bolts from the controller casing!

Now get a hex key and start by doing one rotation on one bolt than move to the next...and repeat till you see the metal ring separating from the gear ring. STOP there.





I didn't have a rubber mallet in hand so I used a rubber handle from a big wrench to tap the square taper end till both parts are detached :

[Sebz]

Remove the axle from the reduction gear and note the direction of the clutch.





Remove the old part, take the gear and inspect it, look at the internal teeth, are they rounded, damaged? if yes get a secondary reduction gear

Clean it, remove all metal shards from the old clutch.

Put the new clutch in the gear like this buy squeezing the spring tabs:






Now follow the same procedure in reverse to reinstall it!

IMPORTANT: when you put back the metal plate over the clutch, make sure you tight the screws in a star pattern, a few turns on each bolts at the time so the plate will go in straight, they need to be really tight so the plate will be sitting flush! If you don't the snap ring won't go in anyways!!!!

Make sure everything is clean of debris, metal shavings ....

If the thrust bearings are dirty, clean them and regrease them! Even is they are clean it doesnt hurt to put little grease in too!


Note: no need to remove the controller to do this, I already removed mine and it's also easier to work without a bunch of wires around!



Seb

[Woody]

Thank you for this excellent tutorial Seb. At 2500 miles my clutch clunk seems to be a bit louder than it was when new and I was hoping to be able to replace it myself when needed. It appears that the procedure for the BBS02 is much more complicated than the BBSHD clutch replacement. Was wondering if it was possible to just grease it without the major disassembly and maybe it would quiet down some.

[Sebz]

Yes it should help, but normally the clutch should not make any sound when you pedal with the motor and the clutch is engaged.

So it might be the secondary gear that needs a little grease!

[squirrelpie0]

Is this the same for BBSO2 A or B?

[Sebz]

I didn't open the ver A, but it should be very very similar (besides the controller shape).

[LI-ghtcycle]

Oops! I guess it was just really stubborn, it eventually came free, thanks for the great write-up!

[jpc6000]

How do I Remove the rubber seal on the axle

[Rider]

Looks like you ply it out with a ice pick or thin screw driver (first photo).

My BBS02B is making a clunking sound during each engaged rotation. I may be checking the clutch pawls soon to see if that is it. Mine sounds like a small piece on metal falling and hitting metal on each rotation.

ADDED: With that said and now having to do it, I'd like to know the trick to getting it out too...

[Rider]

Please add more detail on how to remove the crank seal. Mine has aluminum around the outside. Is it threaded in or just a press fit? Thanks.

[Sebz]

IT's just pressed in, I came across one that was harder to remove, I used 2 little picks (like a dentist would use I guess) and used up all my patience!

[Rider]

Thanks. I finally got mine out with the same thing, sharp pointed scribe.

[pmstirling]

Thanks for this excellent tutorial! I found one on youtube to replace the clutch & gear, but discovered that it's for the BBS02A and I have the BBS02B. After websurfing I found you guys and this tutorial. With an icepick and patience I got the rubber washer out, yay! Looks like I might be able to do this repair myself - I have the exact symptoms of a failed clutch. Hopefully the gear is ok. However I've had the motor less than 2 years, this seems short for the clutch to fail. Is this a known issue, or am I beating on the motor too much? I try to be in a low gear when using the throttle uphill and usually have the assist level only at 1 or 2.

[RandallR]

In my case, this has happened twice then worked again after a time. The pedals spin but do not drive the chain or back wheel. But when I try the throttle the same thing - spins the motor but not the chain. Do you think it is still the clutch? Twice this has happened in the back country and after coasting down a rough hillside, it worked normally again - something loose? Clutch? Any suggestions?

[palumbop]

I just experienced the same problem that you mentioned RandallR. I'm afraid to go to far from home because I don't know what's going on. Seems to be fine now but will probably fail when I'm miles from home. Anyone know what's going on here? Thanks.

[pmstirling]

At the risk of stating the obvious, here goes ...
I had the same thing happen: neither the pedals nor the throttle would spin the rear wheel - pedals just rotated uselessly, and the throttle activated the motor but again no drive to the rear wheel. I assumed it was the clutch and took the motor apart as described here. However the clutch assembly was fine, working as intended. I reassembled everything, reinstalled the motor, and everything worked normally.
Then not long after the same problem happened again. This time I examined the drive train much more carefully, and, d'oh! The chain had slipped off the front crank cog and had fallen between the cog and the plastic guard on the cog. Amazingly invisible, I didn't see it until I looked pretty closely. Simple fix, obviously!
The drive trains from pedals to chain, and from motor to chain, are completely separate. The clutch is only for the pedals, to allow freewheel if the motor is moving faster than the pedals. So there would have to be two independent points of failure for neither pedals nor motor to drive the cog and chain.
I I believe there is no clutch arrangement for the motor, so if you pedal faster than the motor, you will force the motor to rotate faster. This is why there's quite a bit of resistance if you ride with the motor off or on assist level 0.

hope this helps!
patrick

[palumbop]

Thank you Patrick. This might be it! It really bothered me that both the motor and the pedals wouldn't drive the chain. That could never be the case unless as you say the chain had slipped off the front cog. Makes total sense to me now. I will definitely look for this if it happens again.

Thanks a lot!