Bafang CST freehub removal

[RustyKipper]

Hey guys,

As per the tittle I need to service the freehub on my 500W CST hub. It goes through spates of slipping really badly which is a bit worrying as if it fails completely I have a 5 hour walk home from work, or if crossing a freeway I will come to a sticky end.

If I spray penetrating oil down behind the cassette this helps and I can hear the ratchets working again.

I have seen somewhere that removing the two lock nuts within the end of the cassette spline should allow the freebub/spline to pull out but its solid and wont budge, I've tapped it lightly with a hammer but still no joy. It took me a good 10 minutes just to break the actual back wheel free of the frame due to steel/aluminium corrosion so is it possible something similar is occurring with the freehub? Does it maybe just need a bit more 'persuading' with the hammer? This is clearly one of those things that once you have carried out the operation once it is obvious the next time.

Many thanks.

 

[motomech]

As per the tittle I need to service the freehub on my 500W CST hub. It goes through spates of slipping really badly which is a bit worrying as if it fails completely

I don't think the free hub on that motor is removable, but it can be cleaned and lubed by using aerosol and compressed air sprayed down the inside of the spline.
But the free hub is a ratcheting device and does not "slip".
It sounds like you need to look and the clutch.

 

[d8veh]

There's different versions. IIRC, all are removable. Some are dead easy, just remove all the axle nuts and pull it out. Others remoce from the inside of the side-plate, so take all the nuts off both sides of the axle, remove the screws in the side-plate and tap the core out. Then, support the edge og the side-plate on bocks and tap the axle through to separarate it. Whichever method works, you should be able to service the pawls.

 

[RustyKipper]

OK thanks guys, looks like its going to be quite a serious strip down.

The pawls are definitely slipping, the pedals randomly slip about a quarter of a turn of the crank when pedalling forwards, the freewheel clicking sound goes very quiet as well so I'm thinking the mechanism is well gunked up, the bike gets used in torrential rain and deep mud. I might try the oil and airline technique first though.

The motor has now done about 7000 hard miles, the bike has done 12000 miles in 2 years a good portion of this is off road.

 

[d8veh]

OK thanks guys, looks like its going to be quite a serious strip down.

The pawls are definitely slipping, the pedals randomly slip about a quarter of a turn of the crank when pedalling forwards, the freewheel clicking sound goes very quiet as well so I'm thinking the mechanism is well gunked up, the bike gets used in torrential rain and deep mud. I might try the oil and airline technique first though.

The motor has now done about 7000 hard miles, the bike has done 12000 miles in 2 years a good portion of this is off road.

It might be a 5-minute job: take the wheel out, undo two nuts and pull off the hub. I have one like that sitting here in front of me, but there were several different versions of the CST, even though they look the same. The pawls are probably standard bicycle ones, which cost next to nothing.

 

[RustyKipper]

OK thanks guys, looks like its going to be quite a serious strip down.

The pawls are definitely slipping, the pedals randomly slip about a quarter of a turn of the crank when pedalling forwards, the freewheel clicking sound goes very quiet as well so I'm thinking the mechanism is well gunked up, the bike gets used in torrential rain and deep mud. I might try the oil and airline technique first though.

The motor has now done about 7000 hard miles, the bike has done 12000 miles in 2 years a good portion of this is off road.

It might be a 5-minute job: take the wheel out, undo two nuts and pull off the hub. I have one like that sitting here in front of me, but there were several different versions of the CST, even though they look the same. The pawls are probably standard bicycle ones, which cost next to nothing.

How easily do hub/splines usually pull off? I've tried tapping the side of the spline incase its had road salt inside and has corroded but its solid, since trying last I've squirted lots of WD40 down behind the largest sprocket to keep it going hopefully this might have broken the bond., I will have another go at the weekend.

This is a picture of the hub when it arrived from BMS, you can kind of see the very end of the spline under the protective transit boot. I took the photo as the motor arrived damaged but has worked well.

 

[d8veh]

Look down the axle inside the free-hub. There's one or two nuts (round with two flats not hexagonal). Did you remove them?

 

[RustyKipper]

Oh yes, I definitely removed both of these, I remember at least one of them being round with a couple of flats for the spanner, presumably there are no circlips buried down there? I once struggled removing an air conditioning clutch after removing a big but, after much struggling with the biggest puller I could find there was a big bang and the entire front of the compressor broke off, I didn't see a circlip buried in the gunk under the nut....Doh

Am I right in thinking you once had a 2wd bike over there in Telford? I know the hill climbing was good but what was the top speed? I'm guessing about 18MPH. I'm planning something similar this winter as I want to shift some of the weight from the 6Kg rear motor to the front and last winter I kept getting bogged down in thick mud. It would however be a shame to loose the 22MPH top speed of the CST motor.

 

[d8veh]

Oh yes, I definitely removed both of these, I remember at least one of them being round with a couple of flats for the spanner, presumably there are no circlips buried down there? I once struggled removing an air conditioning clutch after removing a big but, after much struggling with the biggest puller I could find there was a big bang and the entire front of the compressor broke off, I didn't see a circlip buried in the gunk under the nut....Doh

Am I right in thinking you once had a 2wd bike over there in Telford? I know the hill climbing was good but what was the top speed? I'm guessing about 18MPH. I'm planning something similar this winter as I want to shift some of the weight from the 6Kg rear motor to the front and last winter I kept getting bogged down in thick mud. It would however be a shame to loose the 22MPH top speed of the CST motor.

If you have those nuts off, it should be just a question of wiggling the hub off. The bearing is quite tight on the axle, so I normally remove the whole side-plate and tap the axle through. It's only 6 screws more!.

Yes, I've had a few 2WD bikes. Each did different speeds. I even had a triple motor one with 5.5kw total. I go to SYEBC in Rotherham occasionally. That must be close to you.

 

[RustyKipper]

Yes the SYEBC is only a couple of miles from me, maybe I’ll pop in next time your over.

OK, think I’ve drawn a blank on this one, the hub refuses to pull off and the screws that hold the side plate won’t budge, well 2 of them undid but the others started to chew up probably because they are so well locktighted in and probably salt corrosion. I think I might be drilling these out. I did however get a good dose of thin oil into the hub spline and the ratchets are sounding much healthier for the time being. I am I bit reluctant to break the side plate seal as my last motor died from water ingress, OK the bearings were sounding horrible for a good while before this!

Interestingly I compared the ratcheting of the CST to that of a standard Shimano XT freehub I have in a spare wheel, the Shimano freewheel is much coarser so must have fewer and larger teeth so the CST will likely be much more prone to clogging up with its finer teeth.

Have you done a 2wd using a Bafang SWXK2 / SWXH combo? I have the former laced into a wheel as a spare already. I know a single 250W will top out at 18 MPH on the flat, I’m kind of hoping a pair might be closer to 20 MPH, I might look at over-volting the motors. The 22 MPH of the CST gives me an extra 5 minutes to get changed when I get home from work at night which is a blessing if I have to get all the wet rain gear off like tonight. The two motors should give the bike a much better balance as well as the little 250W controllers are way easier to conceal and they respond far better to the PAS sensor.

 

[motomech]

Yes the SYEBC is only a couple of miles from me, maybe I’ll pop in next time your over.

OK, think I’ve drawn a blank on this one, the hub refuses to pull off and the screws that hold the side plate won’t budge, well 2 of them undid but the others started to chew up probably because they are so well locktighted in and probably salt corrosion. I think I might be drilling these out. I did however get a good dose of thin oil into the hub spline and the ratchets are sounding much healthier for the time being. I am I bit reluctant to break the side plate seal as my last motor died from water ingress, OK the bearings were sounding horrible for a good while before this!

Interestingly I compared the ratcheting of the CST to that of a standard Shimano XT freehub I have in a spare wheel, the Shimano freewheel is much coarser so must have fewer and larger teeth so the CST will likely be much more prone to clogging up with its finer teeth.

Have you done a 2wd using a Bafang SWXK2 / SWXH combo? I have the former laced into a wheel as a spare already. I know a single 250W will top out at 18 MPH on the flat, I’m kind of hoping a pair might be closer to 20 MPH, I might look at over-volting the motors. The 22 MPH of the CST gives me an extra 5 minutes to get changed when I get home from work at night which is a blessing if I have to get all the wet rain gear off like tonight. The two motors should give the bike a much better balance as well as the little 250W controllers are way easier to conceal and they respond far better to the PAS sensor.

The Phillips head screws are always tight. They need to be removed w/ a hand-held impact driver.
I have both types of the Q100 CST. On the newer versions, the ratcheting spline pretty much falls off when the motor is turned upside down. The other, which appears to be one piece and when I looked at it, I didn't see how it would come apart. You might be wasting your time, like I say before, I don't see how a ratcheting device could possibly slip, but if you meant "skip", then you will likely need new parts and none are available for that motor(That I know of).
In general, using 2 low-'speed motors together will raise the top speed by about 2 mph, 2 mid-speeds, 3mph and 2 high speeds, a wooping 4 to 6mph.
Looking at the pic that was posted, it looks like the spline is cracked all around at the base, or is that an optical illusion?

 

[d8veh]

The hub just pulls off if you wiggle it enough. Most likely, it's just rusty and needs cleaning and greasing, but in the event that the pawls are damaged, I'm pretty sure you can use standard cycle ones. You only need to find ones approximately the same size, they all work the same. They look pretty standard to me.

Here's a photo of the side-plate after I pulled off the cassette hub and a photo of the pawls.






https://www.tritoncycles.co.uk/components-c9/hub-spares-skewers-c122/miche-freehub-pawl-spring-kit-p13704

https://www.universalcycles.com/shopping/product_details.php?id=42877

 

[RustyKipper]

Success!

Finally managed to get the freehub off. I fitted an old cassette and used a pair of screwdrivers to prize the offending part off. The pawls were very much caked in black gunge, most of them were sticking quite badly and the teeth were quite clogged, so I gave everything a good spray with IPA and lubed with EP90 as I'm hoping that might not thicken and clog things up again so soon. Some of the pawls looked a bit worn but the freehub is working like new now.

I quite like the idea of some user selectable gears, the gears have never indexed properly so changed the cassette, chain and chainwheel, the rear mech is fairly new. The old cassette was loose on the freehub spline which I thought wouldn't help. I then changed the gear cable that was starting to fray (these only last 3 months and the shifter 9 months) but after a days fiddling the gears would only index if changing up or changing down but not in both directions ( I hate derailleurs!) I just have to stick to my technique of clicking down twice then up once if I want to change down a gear, its not so bad.

Lastly I thought a rebuild of the pedals was due to try and fix an intermittent cracking sound. These had welded themselves to the arms, even with a blowlamp and lots of WD40 these were not going to let go so stripped cleaned and degreased these while they were still fitted. The pedals are a bit better, I think the mud that got into the bearings over time has not done them any favours. The nasty noises are still there so It looks like a new bottom bracket is on the cards.

The main thing is the freehub is now OK, thanks for your help on this one!