Overhauling a Shimano DH-3N71 Dynamo Hub

[Brucey]

On YACF, every day's a school day.
I can't remove the black plastic seal on the right hand side of the hub. Does anyone know which size of spanner I need? I doubt have one big enough. Today I took it to Homebase but none of their spanners were big enough. Needs to be a ring spanner.

In many cases you need a full octagon spanner to unscrew the internal from a shimano dynohub. Standard spanners and sockets won't work because they are hexagons, not octagons.  Shimano make special spanners for this job. It looks like you could use a headset spanner, but invariably they slip off the fitting and damage it, because they are partial, not full, octagons.

BTW re testing;  apols if this is obvious but with most multimeters if you are testing for current, you need to have the leads plugged in a different set of holes in the front vs volts or ohms, etc.

cheers

[mmmmartin]

invariably they slip off the fitting and damage it

Very easy to do, is that.....

[jimmea]

Resurrection of an old thread...My front dyno hub (DH-3N72) had been running rough for a week or so with a very annoying click and crunching sound. Was going to buy a new one but took it to my LBS who managed repair it by replacing the bearings for £15, nice silent hub now 

[Brucey]

nice result, that; not every LBS would do that and those that would might charge a lot more to do the work.

cheers

[rogerzilla]

My hub is making the unmistakable cracking sound of rusty bearings.  I suppose I have to junk it and rebuild the wheel around a new one, reading this thread.  Are they better now?  I prefer them to the SON28 aesthetically.

[Brucey]

which exact model hub do you have?

With any shimano hub generator the LH bearing is no more difficult to overhaul than any other cup and cone hub, so you may as well take a look at it. The RH bearing is more awkward but you can probably do it if you put your mind to it.

BTW if you have a DH-3N71 and you are giving up with it, I could do with it for spare parts.

cheers

[mattc]

I don't think these pictures have been posted here yet. The photographer ( Mr peterhs64 ) shows admirable diligence and thoroughness!

https://www.flickr.com/photos/28712360@N08/albums/72157643604079324/page2

Album description
Photos of a Shimano DH-3N80 dynamo hub.
They are meant as a supplement to the "Trinity Bicycles" guide to overhauling Shimano dynamo hubs.

This illustrates the unofficial way to maintain the bearings on Shimano dynamo hubs, by taking apart the so called "Internal Assembly".
The critical part in doing this, is to avoid breaking the internal wire running from the stator inside to the connector on the outside through a slot in the axle.
Only the disassembling process is illustrated.

A few of the photos have text descriptions to identify and describe parts or important steps in the disassembling process.