Bafang pedalling issue after installation

Glenntri

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Jan 21, 2022
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I have recently purchased a bafang 750 watt conversion kit on my wife's trek fs4 sportster gravel bike

DERUIZ Mid Drive Motor Kit 750W Electric Bicycle Conversion Kits 8fun BBS02B for BAFANG eBike Central Engine with 48v 52v Lithium Li-ion Battery and Display(Optinal) for Mountain Bike​

68mm bottom bracket and caliper mech brakes
Anyway the kit installed fine ..
44t front chainring and speed and geaR sensor with dpc18 control.
My issue is that the pedalling motion is not fluid like it was half of the pedal revolution it is a struggle to use your feet to turn cranks .usually I have to put one foot under pedal to lift it .the second part of the stroke the pedal moves easily then the stiffness returns on the next half of the stroke...
Thumbthrottle works correctly .
It does this in all pas modes
In pas 0 mode with motor off the cycling effort is unpleasant with the pedal motion being so stiff halfway then easy peasey the other half.
I can't ride this thing like this ...
I even ordered another bafang motor installed it and the same pedalling issue is there...
I removed 2 links from chain when I installed it 10 speed Shimano cassette with index levers
Had to adjust Shimano shift cable after gear sensor install
44t front bafang ring vs 42 t trek small front derailleur
Any suggestions? Programming issue ?
 

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Vinz

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Apr 20, 2021
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I don't think I can offer much help, as it seems you did sufficient troubleshooting. ESPECIALLY since you tried a second motor.
I would pop the chain off the chainring, and turn the pedals by hand. This way you can isolate the motor from the rest of the drive chain. If the problem remains, then it points to a motor problem. But I couldn't guess what kind of problem that would be.
My BBS02 does present some resistance to pedaling, but nowhere near what you're describing.
 

Capt Kirk

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Jan 20, 2022
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I have recently purchased a bafang 750 watt conversion kit on my wife's trek fs4 sportster gravel bike

DERUIZ Mid Drive Motor Kit 750W Electric Bicycle Conversion Kits 8fun BBS02B for BAFANG eBike Central Engine with 48v 52v Lithium Li-ion Battery and Display(Optinal) for Mountain Bike​

68mm bottom bracket and caliper mech brakes
Anyway the kit installed fine ..
44t front chainring and speed and geaR sensor with dpc18 control.
My issue is that the pedalling motion is not fluid like it was half of the pedal revolution it is a struggle to use your feet to turn cranks .usually I have to put one foot under pedal to lift it .the second part of the stroke the pedal moves easily then the stiffness returns on the next half of the stroke...
Thumbthrottle works correctly .
It does this in all pas modes
In pas 0 mode with motor off the cycling effort is unpleasant with the pedal motion being so stiff halfway then easy peasey the other half.
I can't ride this thing like this ...
I even ordered another bafang motor installed it and the same pedalling issue is there...
I removed 2 links from chain when I installed it 10 speed Shimano cassette with index levers
Had to adjust Shimano shift cable after gear sensor install
44t front bafang ring vs 42 t trek small front derailleur
Any suggestions? Programming issue ?
Just looking at your issue, and wondering if your chain alignment is a problem. Are you trying to pedal somewhere in the middle of your rear cassette, or closer to to upper(Large) or lower(small) sprockets. Chain bind will increase the force to pedal. I was force to get a "Blingring"made by Lekkie to correct this, but it was worth it. But remove your chain and see how much force is required to just turn the crank first.
 

Mcwick

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Nov 26, 2021
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It sounds like either a drive train issue or brake alignment rubbing. Spin the rear wheel to check for rub.
 

sojourner

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Dec 1, 2020
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If the crank turns freely with the chain off the chainwheel and the chain does NOT have a bunch of stiff links and the wheel spins when off the ground; your motor must be working against you.....wiring
 
D

Deleted member 4845

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THUMB THROTTLE WORKS CORRECTLY. SECOND MOTOR, ON SAME BIKE, HAS SAME PROBLEM.

Ok, so check pedal fitment, BB mount, test thumb throttle with NO OTHER CHANGES, same gearing, etc.

It ain't the parts that are different motors, so examine the parts that stay the same.

When using the second motor, did you re-use ANY, repeat ANY, parts or mountings or wiring or display, etc, from the FIRST motor, which DID NOT WORK.

When you have an installation that DOES NOT WORK, and you want to test with a second unit to install, then DO NOT repeat DO NOT re-use ANYTHING AT ALL from the first installation.

I know, it couldn't POSSIBLY be THAT, now could it?
 

jhonmartin692

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Apr 12, 2022
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I would recommend you take a look at the programming options for the bike. It sounds like something might be wrong with the programming.
 

Pine_marten

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May 27, 2022
Messages
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8
This would be strange on a Trek, but are ends of the botton bracket square to the bore? The surfaces that the motor tightens against need to be 90 deg. to the crank axle. Are you using spacers? Are they distorted? Try loosening the locking ring and see if that helps.
 
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