IrishBrewer

I am in the process of cleaning up and repairing a kids bike that has a coaster brake. The coaster hub isn't working properly as everything seems to be locked up and the wheel is acting like a fixie in that if I roll the bike forward, it doesn't coast and the crank spins. Also, when I move the crank backwards, it doesn't lock up the wheel but rather just spins it backwards.

The bike was sitting in a basement for probably about 30 years without being used. It has a skiptooth sprocket so that gives you an idea of its age. I'm guessing that the coaster hub assembly is gummed up inside and needs to be overhauled. Anyone ever experience something similar and had luck bringing it back to life?

NYMXer

I agree, sitting for so long, it needs a good cleaning and lubing internally. Corrosion and dust can disable moving parts.
It's easy enough and shouldn't take long

wschruba

Opening it up is, of course, the right thing to do. A possible quick fix, if either the brake or clutch is stuck, is to roll the bike front wheel against the wall, and stomp on a pedal, as if to propel the bike forwards. Repeat, as if to brake, if it doesn't free up from the former.

There is quite a bit of information in the old Sutherland's manuals on coaster brake service/assembly, but given that you are talking about a skip-tooth sprocket, there is a good chance (in the Americas...) that you have a Bendix/Morrow/New Departure hub on there. Beware taking apart a New Departure--there are a lot of small bits to lose.

*edit* To answer the original question: most components that have sat from disuse simply need to be cleaned/relubricated. Of course, if it's been sitting in a barn for 70 years, that's a different story...

55murray

Yep, I bet it is a case of internal grease turning to tar and locking things up - these all have some sort of clutch that moves back and forth between braking and turning. I bet all you need to do is soak the parts, clean and re-lube. Is the skip tooth chain OK? I doubt it has been sitting only 30 years...

cny-bikeman

It's not important or helpful to guess what is wrong, nor to know if it's happened before, as no matter what the problem and overhaul is the answer.

IrishBrewer

Just wanted to make sure it wasn't something indicative of the thing being trashed such that I might as well just replace the wheel rather than spend time overhauling it with little chance of success. I'll try to go over it tonight.

CliffordK

Those things look complicated from the outside, but they really aren't, and can only go back together one way (at least the newer ones).

Just open it up, clean and grease and reassemble. Don't loose parts, or add extras. You probably should be re-greasing it anyway. I think they come apart just by removing the cones and locknuts.

IrishBrewer

Took the coaster brake assembly apart and overhauled it last evening. This has go to be the dirtiest bike part I've ever worked on with tons of caked on greasy dirt on every exposed surface but I got it all cleaned up, re-lubed and put everything back together. Unfortunately, it still wasn't working right when I re-assembled everything. This was a bike from a friend donated to an organization I work for that fixes up and gives used bikes to kids so I have no idea what work had previously been done on the hub.

Next, I looked for a diagram of the hub assembly online and found it. It is a Shimano D-Type hub and Sheldon Brown had some nice links to exploded diagrams and parts lists that was very helpful. As it turns out I had everything assembled properly but the hub is missing a single part. It is the clutch washer (part number 11 on the D-Type hub).

I can find them on ebay and at online parts stores but it will be expensive to buy that little washer shipped to my door. I may check to see if the LBS has one but I was also wondering if anyone could find the measurements of one of these as I could fabricate it on my own by drilling the right size hole in a similar washer. Anyone know how I could get the exact dimensions of this part?
Shimano D-Type Coaster Hub.jpg

okane

Are you sure it's not stuck inside part 12? If insides were as "caked up" as you said, it possibly still could be there.

IrishBrewer

I took it apart again this weekend and it was indeed missing. Instead of paying $6.50 and waiting on delivery for a little washer, I did decide to fabricate one on my own. As it turns out the outside diameter of a standard 5/16 inch washer fit perfectly so I just had to drill out the hole to 3/8 inch and it worked like a charm. Got everything re-assembled and the coaster hub now works perfectly. That washer must be critical in keeping the clutch spring in proper position as without it the spring can seat down too far within the clutch cone.

55murray

Cool! Thanks for the update I was wondering how this went. In similar situations I usually take the parts to the hardware store and start going though the bins...

SquidPuppet

It's not a matter of "down too far within the clutch cone" actually. Without the washer in place, when the clutch cone rotates it "catches" or "is caught" by the end of the spring and they bind and jam up.

Anyway, glad you got it working.