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Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

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Old 04-24-2010, 03:42 PM   #1 (permalink)
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Minitwins
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Gearbox pre-unit

I have noticed that some pre-unit gearboxes have a cable underneath the front running forward
The box I have does not have this

Is this a Speedo cable...?

What years did this cable begin to appear or maybe what year did they remove it?
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Old 04-25-2010, 02:48 PM   #2 (permalink)
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Post some photos please.
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Old 04-25-2010, 09:03 PM   #3 (permalink)
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All pre-unit gearboxes on bikes equipped with nacelles ("49 and later) had a cable coming out of the speedo drive on the right side. Earlier boxes do not have this cable. When the rigid box changed to the swing arm type the cable remained. It was finally changed to the rear wheel with the advent of unit engines. the speedo drive is a seperate unit on pre-nacelle models.
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Old 04-25-2010, 10:21 PM   #4 (permalink)
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Thanks for the info.....

Here is a pic of one with cable...and the Box I have without


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Old 04-26-2010, 11:11 PM   #5 (permalink)
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Quote:
Originally Posted by Rubone View Post
It was finally changed to the rear wheel with the advent of unit engines.
Even unit 650 engines ran this up until about 1965.

The problem was that when you changed rear drive sprocket teeth, your speedo pickup error. Moving the drive to the rear wheel gave accurate readings regardless of gearing.

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