BBS02 Cranks Not Engaging

[Garlic Johnson]

Hi everybody. I'm a newbie here so please bear with me...

I’m having a bit of a problem with a 500 watt 48 volt Bafang BBS02 Kit I installed on an HP Velotechnik StreetMachine Gte recumbent back in May. I just took the bike out for a spin after over a month of not riding it. For the first 15 minutes everything was fine, but as I started to push on the pedals after a red light (I think I was in assist level 3, on a slight uphill, and in one of the higher gears) I heard a banging or cracking sound and felt the cranks spin a bit before catching. The pedaling seemed ok after that, but then it happened again a minute later when I put a certain amount of force (but not an extreme amount) on the pedals. This continued to happen more and more easily for the next few minutes until the cranks no longer engaged at all, and I was forced to ride home using only the electric motor (which seems to work fine). Please help! Right now my bike has been reduced to an electric scooter. The kit only has about 150 miles on it, and before today it had worked perfectly since I installed it. I should add that it has a 52T chainring.
Thanks in advance!!

-G

 

[tommie]

are you sure they haven`t come loose on the splines, its a common occurrence.

your ordinary 2" allen-key is no good, they need a serious amount of torque to stay put.

 

[Garlic Johnson]

Thanks for the reply. I'll take a closer look. The cranks are moving in unison though, so I'm pretty sure they're attached firmly to the motor.

 

[Garlic Johnson]

So, I de-installed and re-installed the motor, making sure to tighten everything completely, and the problem hasn't gone away... Does anyone have ideas what could be going on here? Maybe one of the internal gears is worn down or broken?
Thanks a lot!

-G

 

[speedmd]

Sounds like one of the sprag (One way )bearings is not working. There are a few in this assembly. Look up the assembly in the main bbs thread and it shows them. They make bad sounds like your describing when they go south. It could also be as simple as the screws have come out from the freewheel. Start at page 34. https://endless-sphere.com/forums/viewtopic.php?f=28&t=50104&start=825

 

[Garlic Johnson]

Thanks! I'll take a look.

 

[demeyer1]

Did you ever have any success diagnosing the issue? My brand new EM3EV Bafang is having the same problem, I think.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=72942

I'm wondering if this isn't our problem: http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/front-chainrings-loose-independent-crank-341325.html

 

[speedmd]

You need to check that the screws holding the large gear are not coming loose. You may start to get a bit more rotation when this starts to happen but if only in the pedal/ crank it is most likely the sprag. Don't wait to check it. Post these types of issues on the faults thread so we can better accumulate a trouble shooting guide.

 

[voodoosand]

Did you get this fixed? Was it the sprag bearing like speedmd suggested or something else?

I just had same thing happen, very sad. Fine one day, then crack, bang and nothing - It's definitely something inside the motor housing (AKA not the cassette, chain, rear hub, crank splines).

 

[voodoosand]

Anyone have a suggestion?
I don't think it's the nylon gear, because I can still ride the bike like an electric scooter. Just no human power via the cranks anymore.

 

[speedmd]

Suggestions? Take it apart! You have limited things that this type of failure can be. If the motor drives the bike the primary and secondary reduction gears and sprag bearings are working. BB shaft is connected to the chain wheel via the internal freewheel in the center of the big metal gear on the right side. You have lost the screws that hold one side of the freewheel or the freewheel dogs or springs most likely no longer functioning. Remove the plastic gear cover, remove the lock nuts on the opposite side around the bb shaft and it all slips out on the big gear side. Let us know what you find.

 

[SimplSam]

This is an old thread, but I thought I would reply as I now have a failed BBS02-B (where the crank arms spin but do not engage the motor) and this was the first discussion that I came across that got close to identifying the problem "A failed clutch".

Subsequently -- I found this excellent advice & instructions about replacing a failed clutch - which I am now preparing to complete: https://electricbike.com/forum/forum/knowledge-base/motors-and-kits/bbshd/22903-bbs02-clutch-replacement

I would also say that I am very disappointed with the build quality of the BBS02-B if this type of failure can happen. I have only had my motor 12 months, and only ride electric - a short distances (6 miles) a couple of times a week. On the basis of the nature of this failure - I would never recommend the BBS02.