Gen 4 Rebuild by with pics

[Doomanic]

In Nov 21 I relegated my Rail to second bike status after I bought a Kenevo SL.

In March 22 I decided to try and sell it as I needed the space in the garage. Unfortunately, when I took it out to clean it up for pics I realised that the motor wasn't working; it powered up and walk mode worked but pedalling did nothing. As it was out of warranty I got in touch with @Bearing Man and arranged a strip down and repair estimate.

This was the response;

Water/dirt has got in through the left hand crankshaft bearing which is what typically happens with the Gen4 motor we have found. The crankshaft assembly was semi -seized together as was the left hand crankshaft bearing. Please find attached estimate to repair, if you are happy to proceed just let us know and we will get your motor repaired as soon as possible.

And the quote for repair;

And here's the pics he sent me...

The repair was completed in quick order and the motor has performed flawlessly ever since. I think the cost of repair was fair for the amount of work involved and the turnaround was very fast.

My apologies to @Bearing Man for not posting this sooner, but procrastination is my middle name....

 

[Dax]

That is nasty! Good job @Bearing Man

 

[Tony4wd]

Price seems very reasonable.
Is that dirt that's in the motor or a combination of rust/grease?

 

[Bearing Man]

Price seems very reasonable.
Is that dirt that's in the motor or a combination of rust/grease?

It was dirt! This is not uncommon with the Gen 4 once the crankshaft bushes wear badly.

 

[Tony4wd]

It was dirt! This is not uncommon with the Gen 4 once the crankshaft bushes wear badly.

Can owners tell whether the crankshaft bushes are significantly worn by feeling for movement in the crankshaft? Will the shaft move up/down by a millimeter or two?

 

[RustyMTB]

Great job & a fair price imo. Probably won't ask him to be my wedding photographer though.

 

[Bones]

Interesting about the bushes as mine has a mm or so of play in the crank arms. The shop recons that's acceptable?.
It has done just over 4k hard miles

 

[Ark]

Interesting about the bushes as mine has a mm or so of play in the crank arms. The shop recons that's acceptable?.
It has done just over 4k hard miles

probably time for a service if you wanna see 8k

 

[Ark]

Interesting about the bushes as mine has a mm or so of play in the crank arms. The shop recons that's acceptable?.
It has done just over 4k hard miles

I was just googling if anywhere near me does it for mine when the time comes.

cycletech list it on their website as a service
and they have people all over the country that will collect your bike or do the work at your house.
makes me wonder if they can do a bearing change without sending the motor off anywhere then, maybe even Infront of you whilst you watch and take photos for us

In the middle halfway down this page

Mobile Service Center | BOSCH e-Bike Technicians

Mobile bike repair Shop That Comes To You. Every BOSCH e-bike needs a mechanic once in a while, to make sure that your bike runs smoothly. On-site Service & Repairs.

www.cycletechuk.co.uk

Find one near you Locations | Find a cycle technician within striking distance and ask them

 

[Bones]

Personally I will do it myself. I have an assortment of hammers

 

[Bearing Man]

Because these are bushes and not bearings, you will feel a slight bit if play, even on a new Gen 4 motor. This is usually around 2mm by the time it gets to the very end of the pedal arm.

The picture below shows how the dirt gets into the motor and you can see the plastic bushes shown on our cutaway.

 

[Stevewild31]

If the shop said water ingress from the left hand crank is 'typical' - What can we do to prevent it?

 

[Doomanic]

Move to Utah?

 

[arTNC]

Move to Utah?

LOL!...yes...or west Texas. I know you folks in the UK and other often wet environments would lose a ton of good riding time if you refrained from riding in the wet, so I totally understand. I just won't hardly ride my dirt motor or my MTB/emtb in water or mud anymore. Decades of racing my state's dirt motor enduro circuit involved rain or shine commitment. I just don't have to do that anymore, and the number of dry vs. wet days is favored strongly by the dry days in my home area and yes...southern Utah which I visit somewhat frequently. I'm sure there is still dust/dirt ingress to some degree but at least not accelerated by water. Very interesting thread about this issue and the service that fixed it. Thanks.

 

[Ark]

If the shop said water ingress from the left hand crank is 'typical' - What can we do to prevent it?

Refresh the grease every 6 months or so

Bosch Gen4 Seal Service & Grease up

I made a quick vid on how to save your motor. Hear me speak! In HD!

www.emtbforums.com

Some people have also made comments saying from the factory its possible to have barely any grease behind the seal.

 

[Andrew426]

Because these are bushes and not bearings, you will feel a slight bit if play, even on a new Gen 4 motor. This is usually around 2mm by the time it gets to the very end of the pedal arm.

The picture below shows how the dirt gets into the motor and you can see the plastic bushes shown on our cutaway.

View attachment 136142 View attachment 136143 View attachment 136144

Are there any aftermarket suppliers for that bush? I have my motor apart at the moment, the crank shaft is quite pitted with rust and one of the two bushes is quite worn, causing play in the drive side crank and the assistance to cut out for a split second at a certain point in the crank rotation.

I have an engine rebuilder polishing the shaft and making new bushes for me but I am wondering if there are parts available to buy or if it's a case of buying a new motor if this happens.

 

[Spiff]

Ebike Motor Centre has an upgrade kit, but I believe you will have to send your motor from the antipodes to them for the parts upgrade.

Bosch Gen 4 Upgrade Service - eBike Motor Centre (Performance Line Bearings)

At eBike Motor Centre we noticed a failure pattern on the Bosch Generation 4 motors when used on EMTB’s. We could also see from our own experience, and the sheer number of Bosch Gen 4 motors going through our workshop, there were a few issues that needed addressing, particularly when used...

www.ebikemotorcentre.com

 

[Bearing Man]

Are there any aftermarket suppliers for that bush? I have my motor apart at the moment, the crank shaft is quite pitted with rust and one of the two bushes is quite worn, causing play in the drive side crank and the assistance to cut out for a split second at a certain point in the crank rotation.

I have an engine rebuilder polishing the shaft and making new bushes for me but I am wondering if there are parts available to buy or if it's a case of buying a new motor if this happens.

Yes, these bushes will be soon added to the Bosch parts list. However, if you need some now, just drop me an email through our website.

 

[Stihldog]

I intend to prolong the life of my 2020 Trek Rail with a motor rebuild/upgrade/service after less than 20K kms. Pete has recently posted that an eMTB service centre will be available in NA somewhere (probably in the US).

I have three Bosch Gen4 motors ready to go. Mine is about ready for service. After almost daily use and abuse I know I’m on borrowed time. It’s not making any weird noises or behaving badly …yet.

A motor on my shelf has had the drive-side casing replaced by me. Pete’s distributor in Hull, Quebec (Cyclochrome) provided me with a replacement casing, bearing, bracket and bolts for a very reasonable price. When I opened the motor I had a few concerns. No water ingress. No noticeable wear and tear. Just the colour of the surrounding grease, or lack of grease. This motor is likely due for a service.

The 3rd motor is a mystery to me. It just stopped working. It should be in my hot little hands this week. I’ll probably take a Quick Look inside to see if there’s anything obvious before I send it off for service.

Like some Bosch motor owners I do the best I can to prevent motor failures. Check the motor mounts, bearing seal kit, regular greasing, proper cadence etc. But I still ride in the rain, wash my bike occasionally, ride in the snow, cross rivers and several other abuses.

Maintenance is key.

 

[Andrew426]

Yes, these bushes will be soon added to the Bosch parts list. However, if you need some now, just drop me an email through our website.

Here is a picture of my polished shaft and bushes. My shaft wasn't as badly pitted as the ones in the link another person posted. I have considered putting an oring behind the seal to further prevent water getting in but il have to see if there is space

 

[Bearing Man]

Do not use an O-ring on this application! An O-ring is classified as a "static seal" and should not be used for a rotating application, especially this application because the torque tube (freewheel tube) and crankshaft must be free rotating. Any drag between these two components can cause run-on and may cause the chain to jump of when back pedalling.

Please remember, we would not spend thousands of pounds perfecting a virtually frictionless solution, if we could have got away with an O-ring. We even discovered that a thin film of grease on the plastic bushes, caused big issues with he motor!

 

[Tone461]

When I sent my GFs 3000 ml Bosch motor in to Pete, I was pretty confident it would only require a minor refresh. I knew the previous owner had looked after it and it had never shown any problem at all. There was no play in the crank arms at all, I'd repacked the seals recently, it was never jet washed and my GF is defiantly not a freestyle type of rider, or pedal strikes it a lot (less than me Opps).
When he stripped it and showed me the photos of the motor I had a shock to say the least! Water had leaked past the right hand seal rusting the shaft as in Doomanics post and also showed signs of ingress on the other side. The PCB showed early signs of water ingress as well. Gutted!
I think the damage had been done before I did the seals so I still think its a worthwhile job.

Anyhow, Pete and his team did their magic and now its still as strong as ever, For me, both the motors ( mine as well) are now going to peters as part of a yearly check up. You may think you've treated it well, done all the right things but you might be in for a shock!

 

[Andrew426]

Do not use an O-ring on this application! An O-ring is classified as a "static seal" and should not be used for a rotating application, especially this application because the torque tube (freewheel tube) and crankshaft must be free rotating. Any drag between these two components can cause run-on and may cause the chain to jump of when back pedalling.

Please remember, we would not spend thousands of pounds perfecting a virtually frictionless solution, if we could have got away with an O-ring. We even discovered that a thin film of grease on the plastic bushes, caused big issues with he motor!

OK il forget the oring. So you don't recommend grease between the shafts either? Mine had evidence of grease in it. Unfortunately I wasn't the one to take my motor apart, I just got it back in a box after I paid for a rebuild so I'm not totally sure what did/didn't have grease on it to begin with.

 

[irie]

For me, both the motors ( mine as well) are now going to peters as part of a yearly check up. You may think you've treated it well, done all the right things but you might be in for a shock!

This ^^^

 

[Bearing Man]

OK il forget the oring. So you don't recommend grease between the shafts either? Mine had evidence of grease in it. Unfortunately I wasn't the one to take my motor apart, I just got it back in a box after I paid for a rebuild so I'm not totally sure what did/didn't have grease on it to begin with.

We see very few (4 so far) with a light grease on the crankshaft, but this maybe winding it's way through from the drive gear or excess grease around the right hand crankshaft bearing. The plastic bushes are manufactured from a self lubricating plastic, so grease is not necessary, and if heavy grease is used it will cause drag when freewheeling or back pedalling.

 

[Andrew426]

We see very few (4 so far) with a light grease on the crankshaft, but this maybe winding it's way through from the drive gear or excess grease around the right hand crankshaft bearing. The plastic bushes are manufactured from a self lubricating plastic, so grease is not necessary, and if heavy grease is used it will cause drag when freewheeling or back pedalling.

I have taken it for a quick test ride, only about 20m up the street and back as my shock is away for a service and I've put another one in there that fouls on the frame. But it works. It assists, feels normal, I can back pedal the crank and it doesn't drag the chainring backwards. So all seems well. Il loctite and torque the crank bolts and take it out for a proper ride when my shocks back. Thanks for your help.

 

[Andrew426]

I have taken it for a quick test ride, only about 20m up the street and back as my shock is away for a service and I've put another one in there that fouls on the frame. But it works. It assists, feels normal, I can back pedal the crank and it doesn't drag the chainring backwards. So all seems well. Il loctite and torque the crank bolts and take it out for a proper ride when my shocks back. Thanks for your help.

Fwiw I have done 200km of trail riding on this bike since reassembling the motor (not my main bike) and it performs well, there is no noticeable difference in range or performance and no crank play. I think adding a second green seal would improve the longevity of the motor and could be achieved by cutting 3-4mm (the depth of the seal) off the spacing sleeve and running the drive side bush in further. As it is, I put a bit of moly grease between the flat washer and seal on the drive side of the shaft.

 

[raficzeqq]

Fwiw I have done 200km of trail riding on this bike since reassembling the motor (not my main bike) and it performs well, there is no noticeable difference in range or performance and no crank play. I think adding a second green seal would improve the longevity of the motor and could be achieved by cutting 3-4mm (the depth of the seal) off the spacing sleeve and running the drive side bush in further. As it is, I put a bit of moly grease between the flat washer and seal on the drive side of the shaft.

Hello. I have same issue. Which type of seal for the torque tube did you use?. I cant find anything that fits well with 21,5mm shaft and 25.5mm tube. My motor is taken apart right now and i basically got everything except the right seal. Tried to fit multiple seals without any good effect unfortunatelly.

 

[Spiff]

Hello. I have same issue. Which type of seal for the torque tube did you use?. I cant find anything that fits well with 21,5mm shaft and 25.5mm tube. My motor is taken apart right now and i basically got everything except the right seal. Tried to fit multiple seals without any good effect unfortunatelly.

EbikeMotorCentre has a custom made seal, but I belive you have to ship your motor to them for the installation.

Bosch Gen 4 Upgrade Service - eBike Motor Centre (Performance Line Bearings)

At eBike Motor Centre we noticed a failure pattern on the Bosch Generation 4 motors when used on EMTB’s. We could also see from our own experience, and the sheer number of Bosch Gen 4 motors going through our workshop, there were a few issues that needed addressing, particularly when used...

www.ebikemotorcentre.com

 

[irie]

Our motors were recently serviced and upgraded.

Dropped off our January 2022 Trek Rail 5's to have the motors serviced at eBike Motor Centre

My Large has done over 3,000 miles and wife's Medium has done over 1,000 miles. Now out of warranty so time for some TLC from @Bearing Man "Bosch Gen 4 Motor Upgrade" plus anything else they think should be replaced. Said they need not ask me if something should or should not be done, if they...

www.emtbforums.com