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Bafang BF1808H66200-1 36V 250W Rear Hub

Has your bike lost it’s Oomph, does it now feel like it does 0.0mph extra to your effort?

Do you know how your hub looks on the inside? You can’t tell what lurking in there from the outside…

Has your bike sat for a long time? Has somebody said it’s your battery but you don’t want to believe them?

Does it still make a noise like it want to move but doesn’t? This is your biggest clue maybe, how does it sound?

Did it stop working with no clues or did it give up whilst riding?
The later means you may have damaged something, the former is an indicator of this issue maybe, you see grease ages, it gets old and sticky and parts eventually stop moving, if they do so for long enough then you’ll end up with no drive if your clutch seizes open, or perhaps it’ll jam on and not release, you may hear the motor whir whilst you spin the wheel by hand if it’s still engaged.

The Customer phrased this as

“it just doesn’t do anything on full power, all the lights are on, but there’s no discernible difference between settings anymore, it just stopped working one day, maybe it hadn’t been used for a couple of months. The batteries charged and all the lights come on, but it’s useless on a hill!”

This had me stumped for a bit, but I had a hunch, the strange thing was I’d have assumed and tested further for electrical errors and faults except for the fact the hub made noises like it was still doing something… Just zero discernable torque added with pedal assist at it’s highest level, you could feel a little boost on the flat, but on a hill you’d get zero benefit.

So, what to check first, is it switched on, well yes of course, full battery indicator, all visibly operational, no damaged connectors or wires and some form of response from everything except the power output of the Hub in Assisted Drive modes.

So the strip down begins, the battery removed and voltage checked at 42V so that’s well charged, and looks like it’s not suffering, but I’ve not load tested it or worked out any internal resistance yet, I would almost instinctively think of this to be an issue, it seems odd that the battery level doesn’t drop on the indicator in use. We know therefore the charger also is good. The bike had been left standing in the shop whilst they tried and failed to fault find the issue, so a dud cell could be suspected, but that’s not it.

Hub internals removed, time for inspection…

The wheel has been rebuilt and installed with the axle cutout facing downwards which isn’t ideal, so I go to great lengths to check the continuity of the leads from the 9-pin Juliet Plug to the circuit board solder joints, which appear good, I’m more hesitant of the multimeter I’m using giving false negatives, but it doesn’t appear to be damaged. I’ve full disassembled the hub now and also have the planetary gears visible, these are in good shape although looking a little dry the grease is old and grey but it’s not the issue, it does point towards the age of the hub.

The gears are stuck on the axle shaft and I use a 3-arm puller to remove them along with the clutch, and loose the small woodruff key as I do (easily found, but watch out for it) the twirling and inspecting probably shifted it loose, so be careful as the clutch may float but still need persuading off the axle it gives enough space for it to fall out. Had I realised sooner I might have caught this quicker, but the clutch was off, at this point I’m still running blind, it didn’t function like a clutch should an I just span it and span it, one way then the other, nice and freely it span, little to no real resistance. I secretly knew this was a bit off, but as things were still covered in crap old grease and every part of this hub spins around itself rather freely it wasn’t as obvious to me until I caught a video of someone hacking one apart and I thought all of a sudden about that old grease again.

The sticky old grease in the clutch rollers was holding them back? Maybe, but that leaves one of two options of which either could end in failure, but worth a shot. It’s not an available spare, none of the internals strictly are, it’s sealed and riveted shut in production.
After some moderate cleaning and a blunt tickle it hadn’t got much better but had changed a bit, it got put down and I came back to it and low and behold it jammed on and wouldn’t release, once it released under much load, the was game on!
The second option would involve cutting it open, grinding off the rivets and possibly just riveting it back up afterwards, but I don’t favour the gear shafts staying put for too long, it may become an option next time.

Lot’s of GT85 and a little bit of “engine oil” later, it moves and lives, albeit sporadically operational, it does catch and release, not every time but it’s viable almost, when it grabs though it’d strip the gears so not good enough.
Next come out the big persuader and the flying anvil, oscillating almost syncopated blows on opposing sides whilst giving it a small degree of rotation slowly and then going back to working it round slowly, like checking a bearing for smoothness, or a freehub for engagement.

All of this working it free was done in the vice whilst it was mounted on an old 9mm axle using the cone nuts to centre it with a good clamping force. Using a bar between the planet gear pegs to free it up when stuck again success was judged in the torque required to release it again.

Did it work…

The hub was reassembled with new bearings in the disc / non-drive side and in the planet gears too and low and behold worked as desired first time back on the bike. Sounds good as new, or as good as it’s going to for a hub that’s probably done a good few miles now… Whilst everything looked in almost tip top condition once cleaned up to service it’s not got any noticeable wear except the bearing all feeling like they’d like to have failed a while ago.

Servicing is an important part of keeping your eBike running and we can help you do that, get in touch if you’d like to find out more.

Bike Summary

Bike: Halfords Carrera Crosscity E Folding Bike 250W

Hub Motor: Bafang BF1808H66200-1
Hub Motor Circuit Board:
Planetary Clutch Model: BF180704YA
26T-40T Reduction / 12mm Axle / 9.2mm x 72mm Case x 34mm Total depth / 3x 7.9mm x 20mm Planetary Gear Shafts running twin 688Z Bearings on 17.8mm of shaft.
Bearings (not including Cassette Body freewheel): 6001-2RS for Disc-side x1, 688zz x6 for Planetary Gears

Battery: Reention Rapier IR-III
Li-Ion 36v / 8.7AH / 313.2Wh
GJ-BY36-8K7KPX-01
DBSFSDBY36V8.7AHP180920243

Spares

Spare Parts available through Halfords, although supply may be currently limited the products you may need are available as;

Spare Battery Product Code: 321489 – £300
Spare Speed Controller: Model Year Variants possible; 321885 Battery Controller Unit – £50
Torque Sensor: 299468 – £15
Spare Wheel: 321406 – £150
Handlebar control: 299500 – £25

The Batteries are also offered by a third party on ebay based out of Bristol with a 10.5Ah Upgrade for £359 link here

Fitted to a Carrera Crosscity E Folding Bicycle, it’s built into a 20″ Rear Wheel, powered by a Reention Battery which is honestly worth getting upgraded if it’s the problem unless you really want to avoid the small weight penalty for the gained range.

Some useful videos on similar hubs

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How do you service a BMX? Part 1

Wire Brushed Raw Steel BMX Parts

Servicing a BMX, your step by step go to guide…

 

So your bikes rattling, and a bit stiff, suffered a bit outside and probably a little worse for wear, does it need servicing and some tlc… Have you got rusty Bolts too?
Simple to do you need a strip down and rebuild, it breath a new lease of life into your steed and give it back that sure footed feeling.

Start by giving it a good wash, it’s easier to work on a cleaner bike, even if the dirt looks thin and dry, it’ll shift quickly with a wash and look better once it’s done.

So, first things first, get busy pulling it apart…

Step-by-Step Strip Down

  • Check the seatpost moves, and adjust it a bit maybe to;
  • Pop it in the workstand…
  • Remove the pedals
  • Disconnect the brakes
  • Loosen the Rear Wheel for chain slackening
  • Remove the cranks and Bottom Bracket
  • Remove the wheels
  • Remove the Brake Cables, then pads, then remove the Brake Calipers
    (take care not to separate the springs from the arms, their asymetrical mix them up and your brakes won’t work, worse still you might break  your brakes…)
  • Remove the Handlebar Stem, and Handlebars together, catching the forks
    (watch out! strap a leg to the downtube with a zip-tie to save yourself some toes)
  • Separate the parts on the bars

You should now be left with an almost bare frame… Maybe headset bearing cups and B/B cups remain, the seatpost can come out last, and go back in first, as will any cups you will need to replace.

The Tools Required

So what tools will you need to get this far? Only a few;

  • 4mm, 5mm, 6mm, 8mm Allen Keys
  • 15mm or 17mm / 19mm Spanners
  • Large Adjustable and or Plate Spanner
  • A small screwdriver / pry lever
  • A Cross Head Screwdriver

Now you’ll need to clean all the grime and muck off it, you’ll be surprised where it’s got to… Good old soapy water isn’t a bad start, but there’s good alternatives and GT85 will gut through most grime and grease a lot quicker at this stage.

 

Inspecting the damage

Once you’ve got everything cleaned up, you’ll be wondering whats good and what’s worn out, it’s often obvious but if it’s not I’ll cover it all here.

Deep cleaning, and servicing requires some wire wool, and a wire brush for cleaning any stubborn corrosion.

This is the crown race that’s been abused, and this is the good one replacing it.

The bearing surface should be free from pitting and raised bumps, these will feel bad when your steer and may cause further issues as sudden wear can occur at this point.

Anything that can’t be removed with some wire wool will tell you how you’re doing, if the surface wear is extreme or uneven it’s time for a replacement part.

Acceptable level of wear will show now signs of pitting or degraded surfaces, they should show a polish when clean, you should notice a wear path but it should be free from damage.

If your bearings are at all discoloured, pitted, rusty etc… It’s time to change them too, the retaining cage as well if it’s not cleanable, you can remove it adding extra balls to account for the added room and further increasing the life of the cups.

 

Sealed headsets are a bit different, and will require new bearing sets. These are often one of a few standards so it’s always worth checking the spec properly, they’re often marked with a bearing code for ACB Bearings this is important as the wrong size will damage your frame.

 

 

Cleaning for Painting

 

Wire Brushed Raw Steel BMX Parts
Parts Prepared for painting Wire Brushed Raw Steel BMX Parts

 

 

 

 

 

 

 

 

 

 

 

Painting for Finish

You’ll need a clean dust free, still but ideally open warm air environment but lets be too idealistic about what we want and work with what we’ve got.

Finished & Painted Parts for a BMX Rebuild
Finished & Painted Parts for a BMX Rebuild

Painted Bolts in a Wooden holding block
Painted Bolts in a Wooden holding block

A clean & dust free space will mean your parts have a good finish, even and solid paint finish that will stand up to the fresh abuse it will likely receive.

Applying paint in thin layers working you way around in coats will mean a nice consistent glossy (or matt finish) with good coverage and no drips, focusing too much on coverage will mean overspray and drips… In worst cases it will mean nothing works!

Reassembly of Painted Parts

 

Starting with the Cups if they’ve ben removed, then crowns, the B/B, Headset and Forks are the first things to get installed and we’ll cover that in Part 2, that’s it for now folks…