Oset 20.0 R significant speed loss

[Toby]

My son (8 year, 30kg) rides MX but also has an Oset 20.0 R for technic training at home. It is a MY18 (bought 2019). We are the 2nd owner. I didnt reflect over top speed when I bought it because I didnt knew how fast it should go and had no speedometer. I have had a feeling during the whole Spring that something is not right with the speed. It only goes up to 21km/h while it should be speeding over 50km/h.

 

The bike feels very strong, both when it comes to power and response. But I have nothing to compare to, so maybe it should be stronger.

 

What I have done is, bought new batteries (it didnt help). I also screw down and put together the whole bike (and opened the dc motor) but nothing helped.

 

So now I really need your help, expertise and support. Have you experienced the same issue before? Is it something I can do by my self? Or is the DC motor broken and need to be replaced? It should be mentioned that no strange sound is coming from the bike or motor.

 

Any help appriciated!

[lemur]

Are you aware they generally put an adjustable potentiometer on the control board so you can curb the performance ?

[lemur]

The Oset motors are brush type, the carbon brushes and the commutator that they contact will be the first motor assembly to fail and need service and replacement.   

[konrad]

At first, I thought 50 km/h was expecting a bit much from a kid's trials bike, but that is realistic from a test I just read. 

Although I have no experience with the 20.0R, I also just read that it has separate adjustments for power and speed.   I would investigate the "speed" dial.  Is it adjusted for max speed and not defective?

You mentioned technique training.   I take it your son is not riding it as a trials bike because 21 km/h would be more than enough for backyard trials practice.

[lemur]

You need a VOM meter and know how to use it if you own an electric bike.  Meter test the voltage going to the motor at full twist and if it does not represent the same voltage as the batteries then it must be curbed by the motor controller, if it reads as full volts to the motor and the motor works but performs poorly, that pretty much has to be the motor brushes doing a poor job of powering the magnets.  Adjusting the motor controller to perform at a higher level will make it far more responsive to the point of wheel spin, make adjustments incremental and ride test.

 

[Toby]

16 hours ago, lemur said:

Are you aware they generally put an adjustable potentiometer on the control board so you can curb the performance ?

Yes, it is on max. Also tried to unplug it (thought it will go on max all the time). But then the bike barley moved forward.

[Toby]

16 hours ago, lemur said:

The Oset motors are brush type, the carbon brushes and the commutator that they contact will be the first motor assembly to fail and need service and replacement.   

What is the commutator (main body?). Since the bike is strong in response and power. Could it be the controllerwhich is broken?

[Toby]

16 hours ago, konrad said:

At first, I thought 50 km/h was expecting a bit much from a kid's trials bike, but that is realistic from a test I just read. 

Although I have no experience with the 20.0R, I also just read that it has separate adjustments for power and speed.   I would investigate the "speed" dial.  Is it adjusted for max speed and not defective?

You mentioned technique training.   I take it your son is not riding it as a trials bike because 21 km/h would be more than enough for backyard trials practice.

How do I check if the speed dial is defective?

He uses it more as a MX bike in the backyard track.

[Toby]

16 hours ago, lemur said:

You need a VOM meter and know how to use it if you own an electric bike.  Meter test the voltage going to the motor at full twist and if it does not represent the same voltage as the batteries then it must be curbed by the motor controller, if it reads as full volts to the motor and the motor works but performs poorly, that pretty much has to be the motor brushes doing a poor job of powering the magnets.  Adjusting the motor controller to perform at a higher level will make it far more responsive to the point of wheel spin, make adjustments incremental and ride test.

 

I will do some test with an voltage tester this weekend. But please help me, how do I test the voltage going to the motor at full throttle?

How do I adjust the motor controller, it is just a black box?

So you do not think it is any issues with the controller it self?

[lemur]

4 hours ago, Toby said:

What is the commutator (main body?). Since the bike is strong in response and power. Could it be the controllerwhich is broken?

Commutator is the rotating copper colour metal surfaces that directly contact the carbon brushes.   

There must be videos and/or documentation online by now detailing the steps required to test and make adjustments where you can.  Meter testing for battery power (voltage) and meter testing the resistance (ohms) through wire circuits and ground wire connections back to the battery will confirm it's not just a damaged wire connection, anything that is sealed in a black box (epoxy) is generally not a user serviceable component unless there are obvious adjustment knobs or screw settings incorporated.   Black box assemblies are where you need a second bike or a dealer with access to special test equipment, or known good (new) parts to swap out and ride test.  Any exposed electronics can be visually inspected for burns.  People with electronic repair experience are more likely to know were to look and what components are most likely to fail with age or heat from over-voltage.   Wiring diagrams are always the best place to start, but they will rarely show detailed contents of anything black boxed, for sealed assemblies a second bike to swap out parts to test is unbeatable.  That's how a dealer would easy find all the problems, they would use a bike to swap parts until the problem went to the other bike.

[lemur]

From what I've seen of electric bike fails so far they are often related to the the twist grip assembly electronics on the handlebars.  Which I would guess to be a rheostat control (variable resistor).  I think that is a part I would keep in inventory for replacement after a crash or for trouble-shooting.

[lemur]

Oset technical service videos can be found here if you can obtain permission to view them all: https://osetbikes.com/au/support-en-AU/electric-tech-videos/

edit: for free versions of the videos search the file names, service videos show throttle to use a hall effect sensor, failure rate for the component used in that assembly is high and the video shows how to test and repair the old unit. ... not something I would recommend unless you have a complete replacement assembly and service the old one later.

Edited Friday at 01:38 PM by lemur

[Toby]

On 7/12/2024 at 2:57 PM, lemur said:

Oset technical service videos can be found here if you can obtain permission to view them all: https://osetbikes.com/au/support-en-AU/electric-tech-videos/

edit: for free versions of the videos search the file names, service videos show throttle to use a hall effect sensor, failure rate for the component used in that assembly is high and the video shows how to test and repair the old unit. ... not something I would recommend unless you have a complete replacement assembly and service the old one later.

Big thanks for all the help!

It was a simple issue, but relative hard to find. One of the three cable connectors at the backend of the power potentiometer was broke. You could barley see it with your eyes.

It was hard to find since I had the impression if you pull out any of three potetiometer cables it will always go by full value. This is not the case. When I pulled Speed and Response (with full set on the limit) the bike went down to almost zero in speed and response. But with full set on the limit for Power nothing happened when I pulled the cable. Thats how I figured it out. If anyone else have the similar issue.