Author Topic: Mark 3 rear sprocket  (Read 4253 times)

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Offline milton

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Mark 3 rear sprocket
« on: 03 Jul 2008 at 23:40 »
The rear sprocket on the bike I am looking to restore, has been welded to the drum. This does not seem right. Can't see any other way of fitting a new one. Ideas or answers. Thanks

Offline Doug

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Re: Mark 3 rear sprocket
« Reply #1 on: 04 Jul 2008 at 03:26 »
Milton,

The Mark series sprockets were welded to the brake drum, you were expected to replace the entire drum.

Now days one cuts off and welds on a new sprocket,  risking distortion. Or you mill down the existing sprocket leaving tabs, that you then use to bolt a new sprocket to. You have to pocket the new sprocket so that you maintain the chain alignment. I had to do just that on my Mark 3, I will try to get a picture posted in a day or so.

The Plus series had bolt on sprockets from the factory, but the tabs were offset so that when the sprocket was bolted to the face, it was aligned with the transmission sprocket.

-Doug

Offline Doug

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Re: Mark 3 rear sprocket
« Reply #2 on: 04 Jul 2008 at 16:02 »
The afore mentioned pictures. The original sprocket id cut away leaving six tabs (were the tack welds are.) These have to be faced back slightly, to provide for a corresponding thickness on the new sprocket blank. The new sprocket needs to sit atop the old to maintain the chain alignment.

-Doug








[edit, 'eight tabs' changed to 'six tabs', 05jul08, -Doug]
« Last Edit: 05 Jul 2008 at 19:53 by Doug »