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This is off a neighbour's kid's bike. The pawls weren't springing so I offered to take a look. I've had a couple of similar failures myself and thought I'd open it, clean it, and regrease it. Even with the chain on it felt/sounded dry, more so once I took the wheel off. It was rather stiff to remove, so I doused it in WD40 before getting the pin spanner on it. The whole thing came away in one go.

Freewheel (outside) Freewheel (inside)

Once it was off I couldn't see any way of turning one part against another, but some of the WD40 must have got inside and freed it up, as it had started working again. I added loads of longer-term penetrating oil in the hopes it will keep going, but if it fails again, I'd like to be able to open it up and do a proper job.

So how is a freewheel like this supposed to come apart, especially if I can't turn against the cog because it's spinning freely both ways?

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The outer race (which takes the pin spanner) is reverse threaded. It's impressive that you were able to get it off the wheel with only a pin spanner, but by doing so you have likely made it very tight.

There is no removal tool for this kind of freewheel. Usually to get it off, you remove the outer race and clamp what's left in a vise to remove it destructively.

If you really want to go forward with trying to repair it, grease the hub threads up and reinstall it, then turn the pin spanner clockwise to get the outer race off.

Singlespeed freewheels that lack removal tool fittings are universally low-quality, and usually should just be replaced.

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    Just as well I got it freed uo, because otherwise it would have meant a new wheel/bike. I was expecting a reverse thread somewhere so actually tried the pin spanner clockwise first. It's a 14" kids' bike - everything is low quality, but it's not going to do more than a few hundred km before rusting in a garden after several owners.
    – Chris H
    Commented Feb 21, 2023 at 8:03
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The two dimples on the case cover are the only surfaces provided to grip for unscrewing it. I've never actually found the "correct" tool for this (if there even is one). A pin spanner looks like it would work but they are too narrow and the dimples do not have enough depth.

You need to hold the cog with an immovable chain, such as the chain being in a vise, and hammer a sharp punch into the divot at an angle to turn it counterclockwise.

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  • My Park Tools pin spanner was a perfect fit, but that only allowed me to remove the whole freewheel, and the tool wanted to jump out. It sounds like once the pawls were engaging I should have got a chain whip on it and tried again (or an old chain and a vice)
    – Chris H
    Commented Feb 21, 2023 at 6:43
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I'd wonder if that's a sealed unit, intended to be disposable ? Simply replacing might be a lot less faffing about.

The other option might be to soak it overnight in degreaser/solvent, or a good buzz in an ultrasonic cleaner with degreaser/water solution and hope the dirt can get out.

Third option might be to drill the pin-spanner holes deeper to get a better grip, and hope you avoid any balls on the inside.
Reassembly would need a couple of small goops of epoxy to close up the holes again. Or leave them for adding grease later with a fine-nozzle grease-gun.

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    One of the reasons I offered to look was in case it turned out to be a matter of replacing it, but I forgot to measure the thread. I think I'll have to buy an ultrasonic bath now I don't have easy access to one in work, but I'd definitely want to get grease back in afterwards so the drilling would be "and" rather than "or". Or some fairly heavy oil I guess, but nothing really penetrating
    – Chris H
    Commented Feb 21, 2023 at 6:47
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    @ChrisH NEW TOOL DAY !!! I'm now anticipating a new question "what features should one look for in an ultrasonic cleaner for bike mechanics?"
    – Criggie ♦
    Commented Feb 21, 2023 at 8:22
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    I think it would be a dupe; I've commented if not answered on something similar before. But I don't want to spend loads or take up much space
    – Chris H
    Commented Feb 21, 2023 at 9:03
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    ... but there are 2 litre ones quite cheap that might take a 34T cassette if you used a sturdy plastic bag as the inner vessel
    – Chris H
    Commented Feb 21, 2023 at 9:10
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    @ChrisH You might do better with a vacuum pot rather than an ultrasonic bath: evacuate face-up under a layer of solvent to pull it in, evacuate and warm face-down to push it out, evacuate face-up under suitable lube to pull it in and so on.
    – Mark Morgan Lloyd
    Commented Feb 22, 2023 at 16:56
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TBH I'm not sure it's worth it. Back in the 90s I took my 5-speed screw-on freewheel apart a few times, because I was a student and couldn't afford anything new/better. I got it regreased and back together, but it was always a PITA. These days my money/time ratio doesn't swing that way.

Especially for a kid's bike, they shouldn't be expensive anyway. If it works well enough now, then cool. When it doesn't, it's designed to be replaced, not repaired. (I know how much that sucks for folks like us, but we are where we are.)

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  • With my own, I'm certainly inclined to fix them, because it's an hour or so's work to get it running nicely again. By the time I've taken off a stuck part, measured it up, refitted it temporarily, tracked down a replacement, then got dirty again fitting the replacement several days later, I will have spent almost as long fiddling. But I partly took it off to identify what replacement would be needed
    – Chris H
    Commented Feb 21, 2023 at 9:54

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