Bafang i thin I hate you... ( HALP ME!)

Hi everyone.

Long story short. My BBSO@ shredded a gear. The nylon.



Got a new one. The right one, the 10mm shafted single roller one way Nylon Helical. Fit, put back together, and I got the thing in. Turned it on....


BAfangClunk.

Took it apart. Saw rub marks on rotor.



Rotor was scraping upon reassemble, . Walking. Common problem, So I used this... Anaerobic gap filling sleeve retainer: as per Bruno vids... reassemble, and clunk . Still clunking. I mic'd the journals at 8.01mm.



Tried shimming bearing plates. Clunk..

Checked every bearing, made a homemade BB Puller ( Disregaurd the mess, pls, I hate my lathe too, it probally hates me... ) . Pulled the motor.



Tried removing each shaft individually to isolate the clunk. When the rotor is alone it does not clunk. Only when you assemble the two cases and pull it together with the Intermediate shaft in , It binds and clunk.

Now the magnets are displaced. All of them. They all moved. Are the supposed to move?



When I put the two case halves together, I go nice. But when you bolt the last few threads, it binds and seizes, ( like a side load on the intermediate shaft one way bearing, one-ways dont like side loads... )

I now have seen the inside of my Bafang. Reassembled 10 times. Investigated everything. I know things. Boy would I like to meet the guy who designed this thing. But as for now, I cannot figure this out. Can anybody help me pls?

Ps I read everything I could on here, or at least everything I could find. Note: when assembled, if you load up the final drive, the clunk goes softer, but not away totally. Should I just live with it and try to put it to service? It doesnt sound right at all. Does the drive require a load not to klunk?

I do not want to throw new parts at it without knowing if they will work. ANY help appreciated. If I cant fix it Im buying a qs205. This week.


This drive has 480 miles on it.

I'm no bafang mechanic but i can tell you that seeing these broken is no surprise.
You may be able to fix it but another part will eventually go. The drive has multiple weak points. Over half the parts are known to not be strong enough for perpetual use.

If you have access to machine shop goodies, i'd start considering making your own mid or direct to rear sprocket chain drive instead of messing with these lower cost mid drives. They just seem to be a headache for a lot of people.

Or yeah, from a reliability standpoint, can't go wrong with a direct drive hub... but you don't exactly need a boat anchor QS motor to do what a 750w mid drive did..

neptronix said:

I'm no bafang mechanic

If you have access to machine shop goodies,

They just seem to be a headache for a lot of people.

Or yeah, from a reliability standpoint, can't go wrong with a direct drive hub... but you don't exactly need a boat anchor QS motor to do what a 750w mid drive did..

Click to expand...

Thank you for the reply. I have read extensivly here. I took it to my dad who IS a full fledged competent machinist, for any input, and he took a look, right away said it is probally a " quirk of the machinery manufacture" and " probally not fixable witout a new case..." .... and that is rare. He usually can fix anything. Helps build 8 foot tall Walking beams for rich steam enthusiasts.

Needless to say Im still gonna try a little more. Even though it was not the 6000Km + that some put on these drives. Gonna replace the bearings on the rotor, make a dummy shaft, check tolerances,... Maybe x-ray it or something, and XFR it, ... maybe plastigauge something if I can find something to plastigauge... Lol. yeah right. Nevermind.

Near brand new rotor walking to the point of cracking magnets by now.

I am very familiar with mechanical and rc brush less things... I have a UHD freewheel here and am gonna use it someday ( thats the plan). Maybe some day I will use this ( Bafang) reduction and final drive to build a homemade mid drive if I cannot fix it. I want to go with QS because of the reliability record, and 205 cause it ha a resale value.



Bafang, I was in love with you for a little there, though. Hmm. Probally doesnt help that I destroy every transmission on a bike Ive ever had. Last one ( before this ) was a ZX9 Kawasaki. At least that one works again.

I was going to say it might be built on a friday ( bad case or something else ).. because it sounded like you gave it a hell of a try..

The QS is enormously heavy and many smaller DD hubs can be just as reliable.. and a little more efficient and a whole lot lighter.

Hey Dogdip, dont forget to take that key out of your three jaw chuck Thats a big no no there man,even for a moment .....wayne

I've read too many Bafang Middrive horror stories and issues to imagine that there is any comparison to the robustness of a simple hub motor system. Why do people bother?

For every Bafang horror story, there are probably 100 others who are happily and reliably motoring along. If you're blowing up transmissions on 900cc sport bikes (and every other ICE bike you've owned), I assume you're pushing a little Bafang motor to its limits. If you're after crazy power, get a massive hub motor or a high-power mid (Cyclone, Tangent, etc.) Perhaps you're just looking for more than what a Bafang can provide.

I know. Prolly.

I got it back together. There were no chuck-related injuries, ( had my share of those, Ty)... but it took a little "surface grinding" on the actual rotor. It would still bind on the last mm of closing the case, and then rub the rotor even with every other shaft removed.... I need a new rotor, or a new case. Something is wrong. It has gone 12 miles since. Im staying in the lower gears... the day I tore the gear I was also skipping on 14s lipos when I was on the 11T sprocket @ 20+ mph. So much that I couldnt use it that day. This is 450 mi in the cold on a brand new bike total...

I had a Cyclone motor, and setup, sitting right next to a BBS02 setup, once upon a time. I chose efficiency ( lol ) . I wanted a lower output for my chains sake.. ( not to mention my two wheeled history ),.... Oh well.

I turned down the start current for the throttle, I lowered the amps to 22, I got it back together, and it tests ok under load. However, the one way in the new Nylon gear was slipping on a hard start until I changed from "Speed" to "Current",... and then the one way slipping stopped. Seems to be much gentler on the drive. I lowered start current to 1, and it seems to be a-ok for now. I am sure I need a new rotating assy. Some more heat was developed from the increase in stator air gap and corresponding decrease in efficiency.. and I'm going up hills under 10mph now. I really need a smaller front sprocket.

Rotor still walks a little off load. Lil clunk to remind me what pedaling is all about.

I might have a bbs02 case hanging around here, from a dead bbs02 if you're interested. Pay shipping and the dead bbs02 is yours.
It's from a customer's bbs02 that has lost a lot of varnish on the stator and has a broken main gear shaft after a year of use.

The bbs02 would be downstairs if i didn't chuck it in the trash. Let me know, and i'll figure out how to get downstairs ( currently on crutches ).

Yeah That would be great. Ive been trying to find one, but no avail. Messaging eBay memebers to see if they have one. If I dont use it I would pass it on of course. I got some money invested in this thing lasting at least through the summer, and kinda dread the Nickel-and Dime-ing. Ill pm you in a little,. Ty... I dont really what to do next other than that... and a new rotor,.

Welp, that was fun. 60 some miles later this happened....





Made it home, though. 8 miles hanging a foot off the crank arm and bashing gears.

Can anybody recommend replacement crank arms? Ones without sucha " reputation" ...?


TIA. Jp

DogDipstick said:

Made it home, though. 8 miles hanging a foot off the crank arm and bashing gears.

Can anybody recommend replacement crank arms? Ones without sucha " reputation" ...?


TIA. Jp

Click to expand...

I use Shimano FC-E6000. Cheap and better quality over Bafang. Only problem is to find them in stock, had to import mine from Germany. My original got bent when the bike fell to its side...

Yeah, i had that problem within the first couple hundred miles.

I'm sorry to report that i chucked my dead bbs02. I just hobbled into the garage and could not find it. Sorry to tease you with the prospect. If you post a items wanted ad on this site you'll probably have no trouble finding a dead bbs02 tho.

I just installed the original (1974) Suntour square tapers from my bike. They seem to have the same dimensions as the Bafang ones, leading me to believe they're nothing special.

DogDipstick said:

Can anybody recommend replacement crank arms? Ones without sucha " reputation" ...?

Click to expand...

It looks like you put the right arm on the left side. Pedals unscrew themselves and fall off when you do that. The Wright Brothers (yes, those Wright Brothers) invented the left-hand threaded left side pedal to prevent what happened to your bike.

Any unicycle cranks will bolt right on.

Make sure the cranks are on the correct sides and the pedals are adequately tightened.

Actually the threads on the bafang crank arms are horrible. So is the interfacing to the drive unit itself. I had multiple parts get loose on me.

neptronix said:

Actually the threads on the bafang crank arms are horrible. So is the interfacing to the drive unit itself. I had multiple parts get loose on me.

Click to expand...

The square taper interface to the drive unit has a vulnerability to loosening (due to reversing torque through the taper) that a correctly used normal bike crank doesn't have. There's no getting around that except to check the bolts every so often.

But even iffy pedal threads will stay tight if they're tight enough and used on the correct side. (Fixed gear bikes excepted, because of their reversed cyclical torque through the pedals.)

If you enlarge the photo and scrutinize the pedal threads, you'll see they're RH. That's a right side pedal used on the left side. It's a predictable failure, not a fault of the equipment.

Chalo said:

DogDipstick said:

Can anybody recommend replacement crank arms? Ones without sucha " reputation" ...?

Click to expand...

It looks like you put the right arm on the left side. Pedals unscrew themselves and fall off when you do that. The Wright Brothers (yes, those Wright Brothers) invented the left-hand threaded left side pedal to prevent what happened to your bike.

Any unicycle cranks will bolt right on.

Make sure the cranks are on the correct sides and the pedals are adequately tightened.

Click to expand...

.....



You know what, Im embarrassed to say this. You're right.

Right was on the left left on the right, Hopefully a little sleeve retainer will take care of the thread damage, but it looks like it went back on. I didnt even think to look at the "R" or the "L" on the cranks and pedals when I put it back together the last time. Well, it got me home, and Ill get it back out. Thank you all for the suggestions.

DogDipstick said:

Chalo said:

It looks like you put the right arm on the left side. Pedals unscrew themselves and fall off when you do that.

Click to expand...

You know what, Im embarrassed to say this. You're right.

Click to expand...

It's a very easy mistake to make when the cranks and pedals look exactly the same on both sides. I've seen the same thing with BMX bikes that have RH/LH compatible cranks. Someone has a lapse of attention and attaches the front sprocket to the left crank before installing it on the right, and the next thing you know their pedals are coming off.