Bafang/8fun motor disassembly

Hello everyone, This is my first post here. I am from Sweden and have used an e bike with a bafang/8fun rear mounted motor for a few years now. Heavy usage and harsh winters have taken their toll and the motor has finally given up the ghost( it made a rough rattling noise and then stalled entirely). Anyway the bike store suggested that I replace the whole wheel or just the motor drive assembly alone which would cost between 250 to 300 USD. I declined this since I figured that I could probably repair it myself for way less than that.

After looking around I found that the hub is probably a 250W 8Fun SWXH although im not 100% certain. The problem appeared to be that the nylon planet gears wore down. This is an easy fix since it involves just replacing the gears but I also found that the motor runs quite roughly when spun up just by itself.

The reason for the roughness is probably that the internal bearing(the bearing between the stator and rotor) must be worn down or has clogged up with gunk and pieces of the planet gears.

I have googled around but I cant figure out how to remove the stator from the rotor so I can access the main bearing.

In the exploded view it seems like I have to remove a spring cotter and the three screws to remove the sun gear which will then allow me to remove the second cotter spring and the key which should then free up the rotor from the shaft.



However I cant seem to get the spring cotter out. I have tried to squeeze and remove it with some needle pliers but I dont really see how it slides off the shaft.

I guess the ideal solution might be to make the motor run smooth without opening it. Can I clean the motor with WD 40 or similar and then try to pack the bearing with grease? Sorry if that sounds like a noob question but then again thats exactly what I am

Your help will be very much appreciated!

The rotor is a "press fit" on the shaft. I only tried once to pull it off the shaft with a large gear puller, but only succeeded in bending the rotor. Even trying to heat it didn't help. Even if yours was new, it would be hard to get off and now with the corrosion and all......

If the bearing is dry and rough, then it's races are pitted and adding grease will only help in the short term.

Mini motors are relatively inexpensive, typically a $100US plus shipping. It's possible , if you can ID your motor, to buy the exact same model and swap motor cores, elimitnaing the need to rebuild the wheel.

motomech said:

The rotor is a "press fit" on the shaft. I only tried once to pull it off the shaft with a large gear puller, but only succeeded in bending the rotor. Even trying to heat it didn't help. Even if yours was new, it would be hard to get off and now with the corrosion and all......

If the bearing is dry and rough, then it's races are pitted and adding grease will only help in the short term.

Mini motors are relatively inexpensive, typically a $100US plus shipping. It's possible , if you can ID your motor, to buy the exact same model and swap motor cores, elimitnaing the need to rebuild the wheel.

Click to expand...

Thanks for the post. Thats what I was afraid of I guess. On the bright side it simplifies things since I no longer need to break apart the motor .

I could not find any sites that sold just the motor in europe but greenbikekit.com in the US stocks them. http://www.greenbikekit.com/electric-motor/rear-bldc/bafang-swxh-bldc-hub-engines.html : This looks like the one that I need.

How do I know if I need the sensored version or not? There does not appear to be any circuit board or anything that looks like a sensor on the motor - just the coils etc.

Also, how can I be sure that it is an SWXH motor? I'm wondering if I should buy a controller to go with the motor just in case the one that I order is the wrong version is non-compatible with my controller.

A SWXH with sensors will have 8 wires coming out of the axle. Three are heavier and are the blue, green, and yellow phase wires. The other five are thinner and are red/black for power/grond, plus blue, green, and yellow for the Hall sensors.

A sensorless motor only needs the three phase wires.

First off, Green Bike Kit is in China. There is also BMS Battery and Elife Bike to check.

You want sensored, especially w/ mini-motors. If your current system is not sensored, I would think about a new controller as well. Actually, controllers have come a long way in the last 3 or 4 years. The new Sine wave controllers with 5-level "torque imitation" PAS are game changers for those riders who like to pedal.

Also, there are some geared motors that have dedicated seals on the axle that are more "weather resistant". But no mini's that I know of. Just larger, more expensive motors like the Ezee and the BMC.
But knowing what you know now, I guess you will be taking your new motor apart and cleaning it after the winter season.

Oh, by the way, I am running a Bafang SWXH in the rear of my wife's ebike with a BMSBattery S09PW controller that is sensorless. I bought it w/o noticing it was sensorless, but it works fine with the Bafang.

docw009 said:

A SWXH with sensors will have 8 wires coming out of the axle. Three are heavier and are the blue, green, and yellow phase wires. The other five are thinner and are red/black for power/grond, plus blue, green, and yellow for the Hall sensors.

A sensorless motor only needs the three phase wires.

Click to expand...

In that case mine is the non-sensored version. I had always thought that there must be some kind of speed feedback into the controller for it to limit the bikes speed to the legal 25 km limit here in europe. since mine does not have a sensor im guessing that the controller works by limiting the peak power roughly to that which is needed to achieve 25 km/h.

motomech said:

First off, Green Bike Kit is in China. There is also BMS Battery and Elife Bike to check.

You want sensored, especially w/ mini-motors. If your current system is not sensored, I would think about a new controller as well. Actually, controllers have come a long way in the last 3 or 4 years. The new Sine wave controllers with 5-level "torque imitation" PAS are game changers for those riders who like to pedal.

Also, there are some geared motors that have dedicated seals on the axle that are more "weather resistant". But no mini's that I know of. Just larger, more expensive motors like the Ezee and the BMC.
But knowing what you know now, I guess you will be taking your new motor apart and cleaning it after the winter season.

Click to expand...

what are the benefits of going sensored and of the new sine wave controllers?

I saw some of your other posts on the since wave controllers and what I gathered was that they are more efficient, quieter, better response etc.

I will probably use some gasket maker to make a tighter motor seal. It is a four year old bike and has spent the last 2 winters parked outdoors with almost daily usage so I was honestly surprised it lasted so long. Our roads are heavily salted during the winter and a lot of the salt ends up on the bike paths so im sure that played a part in the corrosion. Preventive maintainance might have got more life out of the bearing so all in all im pretty impressed with the little motor .

I would love to get a 350+ Watt motor but since Swedish law does not allow them to be used on bicycle paths I would be forced to ride on the main roads. Not the best place to be for a cyclist during the winter when its dark most of the day.

what are the benefits of going sensored and of the new sine wave controllers?
I saw some of your other posts on the since wave controllers and what I gathered was that they are more efficient, quieter, better response etc.

Click to expand...

That's a big topic, that has been covered here at length, but to my way of thinking, it's the improved PAS Experience. You have heard of the expensive systems like the Bionx, that measure the rider's input at the crank and feed in the motor power proportionaly. Well, the inexpensive 5-level "torque imitation" systems simulate this and offer a much better "feel" to the rider using PAS. So much so, most riders don't use the throttle at all.

I will probably use some gasket maker to make a tighter motor seal. It is a four year old bike and has spent the last 2 winters parked outdoors with almost daily usage so I was honestly surprised it lasted so long. Our roads are heavily salted during the winter and a lot of the salt ends up on the bike paths so im sure that played a part in the corrosion. Preventive maintainance might have got more life out of the bearing so all in all im pretty impressed with the little motor .

Click to expand...

The harmful agent is the salt and it's coming in though the bearings on the axle, not though the motor cover. The best preventive measure would be cleaning the insides w/ a spray lubricant at the end of the Winter season.

I would love to get a 350+ Watt motor but since Swedish law does not allow them to be used on bicycle paths I would be forced to ride on the main roads. Not the best place to be for a cyclist during the winter when its dark most of the day.

Click to expand...

Who would know? The 350 Watt Q100H is in fact, smaller than your current motor. And I think 250 Watt stickers are available at PedelecsUK or on EbayUK.