Tongsheng TSDZ2 racing and overheat


I have a Tongsheng TSDZ2 which I have put about 4,000km on. I've had a few niggles with it, (which I mentioned in a thread titled Tongsheng Grinding) but it moved to a new level recently. This added to some existing clicks and grinds, which tended to get worse during a ride.

After a freewheel today, the motor gave the impression of a slipping clutch on a car, with a racing sound from inside. This developed into a steady ugly-sounding whine, accompanied by a loss of power. When I finished the ride, on a hunch I checked the motor for temperature. It was boiling hot, too hot to touch.

To be honest, I have only done minimal maintenance on the motor, given that I am not confident fooling around in the innards of these motors. It could be something as simple as a lack of oil, I suppose, but I really have no clue.

But clearly I need to take some action now, and if anyone has any ideas on what bits of the motor I should check and what remedies I could apply, I would be most grateful.
I think you will have you be replacing numerous mechanical bits, like the clutch, Look on youtube,
After 1000 miles, my TSDZ2 has started to show some lateral play in the pedal axle. I can grab the base of either pedal arm and wiggle it back/forth about 1 mm. Sign of cheap bearings, I guess. Does yours do this?
Not sure about the lateral play, as I never checked before dismantling the bike, but what you say makes sense as the pedals don't always feel solid.

I didn't even realise that the Tongsheng had an actual clutch, I was just describing symptoms of how it felt.

Given my general ignorance, I think I will have to retreat to a hub motor set-up or splurge on a CYC Photon where I can expect some service help if needed.

I'll go ahead and rip the motor to bits tomorrow to see what damage is visible, in case it helps other posters in similar situations.
Just following the thread, but I would definitely like to see the pics from the tear down to see how the motor is put together.
I wouldn't be hesitant to take the tsdz2 apart. Everything is very easy to do and other than snap ring pliers I don't recall any special tools needed. My guess is that the plastic gear on the non-chainring side has stripped or the tiny clutch bearing pressed into this gear has failed. The only other "clutch" in a non "B" version is the sprag clutch in the large gear on the chainring side of the motor. There isn't any need to remove the motor from your bike unless you want to. Parts prices seem to fluctuate but overall easy to source and usually inexpensive. I bought a spare plastic gear a couple years ago for less than $10 on but have never had a need to use it and I'm confident that if I was on a tour ride I could replace it roadside in not much time. There is a metal gear available to replace the plastic one but reportedly is louder. The large gear with a sprag clutch bearing on the chainring side is more expensive but still reasonable last time I checked ~$50. If you have a Harbor Freight type shop press you can just replace the bearing itself pressed in the gear. There are good youtube videos on how to do any of this.
Regarding the axle bearings, they look like standard bearings that could be purchased on amazon for a few dollars. Simplicity and availability of parts is one of the strong suits of the tongsheng.

the large gear on the chainring side shouldn't be the issue on your bike because the sprag clutch bearing pressed into it only engages to allow your pedaling to assist the motor and disengages when you stop pedaling. the small plastic blue gear on the non-chainring side (with a tiny internal clutch bearing) is what transmits motor power to the large main gear and is likely your problem. Again, simple to access and replace.
Many thanks for the detailed and informative reply.
Because of the lack of lube on the main gear and step-down gear on the drive side along with water incursion, the needle bearings inside the blue gear have lost their chrome finish due to over stress. Clean the non-drive side of the blue gear's shaft and reinstall that side with a new gear and use plenty of white lithium grease. The plastic cover of the main gear is attached by four 2.5mm hex cap screws. Your main gear is dry and rusted. I always pack the main gear and stepdown gear as part of motor prep before installation. Use molly grease. It makes the motor quiet, more powerful, and it keeps out water. Just pack the cover and reapply after cleaning off the rust. See if there is rust on the motor, I bet there is. If so that indicates that the torque sensor is about to fail. I avoid that as part of prep too.


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OK, so I opened the thing up this morning, with rather depressing results.

The chain side looked much as before, and the two gears rotate smoothly together.


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I then took off the main cover on the non-drive side, and saw .......

.... some rust, but mainly out-and-out corrosion of the entire thing. I could put that down to several factors: one, it is extremely hot, humid and often wet where I live; I have neglected to do proper maintenance on it; water seems to get in to this motor remarkably easily.


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I looked for anything further I could do. Looking from the top, there are those six small screws, though that doesn't seem to be more than just a cover


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At a slight angle, there are a few cross-head screws further down.

And here is where the problems start. I don't know which set of those screws to undo, and even if I did, they seem completely immovable with the tools I have here, whether they are rusted on, or deformed.

This is as far as I can get. I dare say a well-equipped shop with all the right equipment could make something out of it, but unless I can come up with some cunning plan, that's where it rests for now.

A lesson, perhaps, on the need for regular maintenance and water management.


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Man, that picture of your motor sure looks bad. Maybe it's time to get another one.
On the plus side, you'll get some free parts--and the priceless experience of taking it apart.
Man, that picture of your motor sure looks bad. Maybe it's time to get another one.
On the plus side, you'll get some free parts--and the priceless experience of taking it apart.
I like the motor, especially with my 500C display, but I am concerned at how easily water got inside the motor and caused such corrosion.

While I'm trying to fix the Tongsheng, I had to rebuild my old hub drive cadence sensor bike. It feels completely alien to ride, the complete motorized scooter. Funny I never noticed that when it was my only experience of e-biking.....:)
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Maybe it's time to get another one.
The drive side has no grease. The motor side is rusted, indicating a host of other problems. I like EMXG's point about penetrating oil, maybe with a little heat for expansion before application, so it gets sucked in with contraction. It takes a fresh #2 Phillips. I like to make the handle wider for better torque application. But this unit looks like a forever problem that is not worth the frustration. It would be throwing good time and money after bad, IMO. It is probably better to walk from the poker table than to double down on a lost cause. Take what you have learned from this one to fully prep the new motor when you are ready. There was a batch from a supplier during the pandemic that forgot to prep the O-ring on the motor side. How can you keep shutting down a factory and restarting, again and again, to pickup exactly where you left off each time?


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While rinsing one of my bikes today with a low pressure hand sprayer a thought popped into my mind that I cannot get rid of. The bike has been exposed to a pressure washer something like five-times. If that is the case, then the rear wheel hub is also about to fail. It may already be making coffee grinder sounds. I wish @RickBradford the best. Yes, there is nothing wrong with opening it up, if for no other reason as an anatomy lesson in failure analysis. Obviously I learned my lesson about power washing the hard way and that is why the horror show of disaster awoke. Once you have seen it, it doesn't go away, like PTSD flashbacks.
Update: I finally got the right tools and after a certain amount of marination in oil, I got the thing apart. The plastic gear doesn't look, to my amateur eyes, to be too bad - certainly not stripped, but maybe a bit worn at the edges. It seemed to mesh and rotate with the metal helical gear OK, but obviously that's without any power being driven through it. The casing was covered in a white grease of some sort.


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It obviously shows signs of use, some water ingress and rust, but the internals look, well, functional.

So, all in all, I'm not sure what's going on.


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I just pack the inside of the main gear cover with grease and press it on. I use something similar to silicone plumber's grease on the O-ring. The stuff I use is for a different application, same stuff, comes in a big tub but is not rated as food grade. The plumber's grease holds up under pressure inside faucets. Butter up both sides. With the white gear, it is not the outside that is bad. The needle bearings on the inside of the white gear have been de-laminated of their chrome. It is all crunchy in there.


Pretty sure the white plastic gear in the newer B version doesn't have internal needle bearings. They were present (one way bearing) in the older blue version, like I have. The white plastic gear should be fixed and not moveable on the reduction gear shaft. If I understand correctly that was the major change from the older to the newer B version - function of the tiny one way bearing in the blue gear was incorporated into the second one way bearing in the large main gear on the chainring side. Thereby eliminating the need for the smaller, more fragile bearing that had been pressed into the plastic gear.
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I just inspected one. You are correct. I was wrong. The white gear is fixed to the stainless shaft. That is why peer review is good.
Well, having taken the thing apart, I greased everything in sight and put it all back together again. Miraculously, it worked fine and - no noise!

So, whatever was causing the problem seems to have been fixed. Trouble is, I've no idea what or where the problem was, so I've no way to know how to prevent it happening in the future, except by being a bit more proactive with my maintenance.