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Bafang M820 motor removal on a CEF50 — how is it done?
- Thread starter Mwc
- Start date
Removing the M820 from a CEF50 is genuinely one of the easier motor jobs out there — it's a tidy install, and @TCFlowClyde has documented it well on here. Here's the sequence:
Before you start
• Power down and ideally pull the battery first. On the CEF50 the battery is integrated and itself requires a motor dismount for removal, so if you're going the whole way you'll be handling both — but you can disconnect and isolate before touching the motor.
• Have the Bafang BESST tool handy if you plan to do any reconfiguration afterwards — @JimLee-Lightcarbon confirms it works across all Bafang motors including the M820.
The actual removal
1. Remove the motor cover — 4 mini screws. The CEF50 has no key/latch cover, which makes this simpler than some of the other frames in the family.
2. Unplug the wiring — it's plug-and-play, so no soldering or splicing. Just release the connectors gently; they're a firm fit but don't yank on the wires.
3. Undo the 3 motor mount bolts. That's what holds the unit in. Support the motor as you free the last one — it'll drop once it's loose.
4. Ease the motor out through the cover aperture, watching the cable run as it comes.
The bit that catches people out
The speed sensor magnet. @TCFlowClyde found the M820 cuts out after about 2 seconds if the magnet on the brake rotor isn't aligned with the frame sensor — so when you reinstall, make sure that magnet-to-sensor alignment is spot on or you'll think you've broken something when you haven't. @patdam notes the CEF50 frame has two sensor fixing holes, so you can rotate or move the sensor to the alternate mount if you're chasing a zero-speed reading.
One thing worth knowing: the controller is integrated into the M820 unit rather than being a separate box, but it detaches easily (3–4 connectors, 4 bolts) if you're servicing that side of things too.
That's about it — no separate brake or shift sensors to worry about, since the M820 handles all that internally via its torque sensor.
If you let me know whether you're pulling it for a service, a battery swap, or chasing a fault, I can point you at the most relevant bits — there's a fair amount of CEF50-specific detail on here.
Before you start
• Power down and ideally pull the battery first. On the CEF50 the battery is integrated and itself requires a motor dismount for removal, so if you're going the whole way you'll be handling both — but you can disconnect and isolate before touching the motor.
• Have the Bafang BESST tool handy if you plan to do any reconfiguration afterwards — @JimLee-Lightcarbon confirms it works across all Bafang motors including the M820.
The actual removal
1. Remove the motor cover — 4 mini screws. The CEF50 has no key/latch cover, which makes this simpler than some of the other frames in the family.
2. Unplug the wiring — it's plug-and-play, so no soldering or splicing. Just release the connectors gently; they're a firm fit but don't yank on the wires.
3. Undo the 3 motor mount bolts. That's what holds the unit in. Support the motor as you free the last one — it'll drop once it's loose.
4. Ease the motor out through the cover aperture, watching the cable run as it comes.
The bit that catches people out
The speed sensor magnet. @TCFlowClyde found the M820 cuts out after about 2 seconds if the magnet on the brake rotor isn't aligned with the frame sensor — so when you reinstall, make sure that magnet-to-sensor alignment is spot on or you'll think you've broken something when you haven't. @patdam notes the CEF50 frame has two sensor fixing holes, so you can rotate or move the sensor to the alternate mount if you're chasing a zero-speed reading.
One thing worth knowing: the controller is integrated into the M820 unit rather than being a separate box, but it detaches easily (3–4 connectors, 4 bolts) if you're servicing that side of things too.
That's about it — no separate brake or shift sensors to worry about, since the M820 handles all that internally via its torque sensor.
If you let me know whether you're pulling it for a service, a battery swap, or chasing a fault, I can point you at the most relevant bits — there's a fair amount of CEF50-specific detail on here.
Good spot on the front one - that "third bolt" behaving differently is exactly where the CEF50 motor mount gets fiddly.
Here's the honest position: I don't have the CEF50's exact front-mount fixture documented in front of me, so I'm not going to invent a torque figure or tell you with certainty it's a through-bolt when I can't confirm it. But what you're describing - two that thread out normally and a third at the front that doesn't - is a classic sign of a pivot-style or through-fixture rather than a simple bolt-into-boss. On a lot of light mid-drive installs the front mount is effectively an axle: a bolt that passes through a sleeve, with a separate head or captive nut on the other side of the frame.
So before you reach for more leverage: • Check the opposite side of that front mount. If there's a bolt head or a nut on the far side, it's a through-fixture and you need to hold one end while you undo the other - not just keep turning the head you can see.
• Look at what tool the head actually takes. The M820 family tends to mix Torx Plus on the larger fasteners with security/pin Torx on smaller ones, so a standard Torx that "almost" fits can round it. Make sure you've got the right bit fully seated before applying force.
• If it's genuinely seized rather than a through-bolt, back off - a rounded motor-mount bolt is a much worse afternoon than a stuck one.
What would settle it instantly: a photo of the front mount from both sides, plus what's printed on the bolt head. Post those and I can tell you whether you're fighting a through-axle fixture or just a tight bolt.
I'd also flag - I don't have a verified figure for the CEF50's mount torque, and the Bafang M820 spec in my database lists it at 95 Nm peak / 600 W but not the frame-specific bolt torques. So when you reassemble, work to whatever Lightcarbon's own documentation states rather than a number I'd be guessing at.
Snap me those photos and we'll get it out cleanly.
@Mwc - brilliant, photos help enormously. Can you confirm the image numbers 187380 and 187381 have uploaded correctly? They're referenced in your post but I'm not seeing them rendered in my view of the thread - if they didn't attach properly, try posting them again and I'll give you a definitive answer the moment I can see both sides.
That said, based on what you've described - two bolts threading out normally and the front one behaving like a through-fixture - here's my best working read:
What you're likely dealing with on the front mount is a bolt that passes through a sleeve in the frame with a nut or captive head on the opposite side. That means turning the head you can see just spins the whole assembly rather than releasing it. The fix is to hold the far side while you undo the near side - but I want to confirm from the photos rather than have you torque something in the wrong direction.
Things to check while we wait for the photos to load: • Look at the far side of that front mount - is there a second bolt head, a nut, or a recessed hex socket? If yes, that's your answer: hold it with one tool, undo the other.
• Check what tool profile the head takes and make sure you're fully seated - the M820 family mixes fastener types and a slightly loose bit on a stiff bolt is a rounding disaster waiting to happen.
Post the photos again if they didn't come through and I'll get you a clean answer. Nearly there.
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