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Discussions Question and Answer Forums Electric Scooter, Bike, and Go Kart Repair Forum

Chain Problem

Hi guys,


I have a problem with my chain, although not sure if it is the chain itself.

What happens is with each rotation of the wheel, the chain loosens and tightens.

One half of the rotation it's loose, the other half it's tight, it goes like this, too tight, optimal and then too loose.

I dismounted the wheel and I can't seem to find the issue here.

Could anyone here tell me where I could start.

The wheel is mounted straight.

One thing I like to mention, there is a lot of resistance coming from the motor. When I rotate the wheel by hand, it's very hard to do so. Also, it's easy to turn by hand on one part of the rotation, and on the other it's much harder to do so, could this be to do with the motor? However even if it was, could it explain why the chain is changing from loose to tight?

I have an Evoscooter 1800W by the way.


Thank you very much

This type of problem could be caused by a:
  • bent motor shaft
  • bent wheel hub
  • bent sprocket
  • improperly machined wheel
  • improperly machined sprocket.
I suppose it could also be caused by loose sprocket mounting bolts or a bent axle.

I would rotate the drivetrain and carefully inspect all of these parts to see which one is wobbling or out of true. That will point towards exactly which part is causing the problem.

Please let us know how it goes.
The wheel and sprocket are definitely machined and mounted on properly. I carefully inspected it and the only thing I found is that some teeth on the rear sprocket are smaller than others. Perhaps this is due to the sprocket bring manufactured incorrectly? I guess this would be the only solution to this problem? Replacing the sprocket?
All of the sprocket teeth should be exactly the same size. The sprocket may have been incorrectly machined by the factory or if it has been used for a while then it may have worn unevenly for some reason. Since you determined that the sprocket is the only drivetrain part which has variations in it then that would be the right part to replace.

ive a problem with my chain when the wheel is turned backwards slowly my chain wobbles up and down. at speed it fine only happens when wheel is turned slowly.any ideas,thanks

It sounds like maybe the chain and sprocket are getting worn out. When sprockets wear out they can catch on the chain and make it wobble as you described. It is best practice to replace both sprockets and the chain at the same time because these parts wear out together so they should be replaced together.

thank you esp

when i try to move the rear wheel by hand there is a lot of resistance too much actually, sometimes when I try to accelerate the scooter it cuts off as there is too much resistance. the resistance is coming from the motor itself, it's almost impossible to move the motor sprocket by hand. Im wondering if this is due to regenerative breaking or if the motor is malfunctioning. It is an evo 1800 scooter. also the motor heats up very quickly, even heating up quickly if running the motor while the rear wheel is off the ground. I would greatly appreciate any help with this

Hi Krystian, chances are pretty good that the problem is with the motor itself however it is a good idea to perform some tests before replacing it.

Carefully inspect the five thin wires and their connector between the motor and controller. If any of these wires are broken or short-circuited, or the connector is not making good contact between the wires then that could cause the motor to overheat and run poorly.

Next, disconnect the three thick motor wires from the controller and then try to spin the motor by hand. If the motor spins easier with it disconnected from the controller that points towards a possible problem with the controller, however, if the motor still has the same amount of spinning resistance that it had when connected to the controller then that points towards a problem with the motor.


Please let us know how it goes.

Thank you for the help. All connectors are in good shape. The motor has the same spinning resistance regardless of which wires are connected or disconnected then it must be the motor itself like you pointed out. Is there anything I can try myself or is the motor to be replaced? Thank you again for the help
If the motor continues to provide excessive physical resistance with its wires disconnected from the speed controller then the problem would have to be with the motor itself and not with the speed controller.

You could try disassembling the motor to try to find a problem such as bad bearings or a loose component inside of it. Or if you think it is beyond saving then just replace it.
I have finally got around to disassembling the motor. I have taken out the magnet core and to my surprise one of the arc magnets was broken! This was why there was so much physical resistance coming from the motor. I am wondering where you can buy such an arc magnet. I also put a picture so you can see. It is a Boma motor 48V 1800W. I can't find any of these very specific magnets online. I would appreciate any help!
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Does anyone know where it's possible to buy the core itself if you can't buy the arc magnet? Thx
We are not able to get rotors or rotor magnets for those type of motors and can only get the whole motors by themselves. Maybe someone else here knows though.
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