Rear sproket/wheel play mk3

Last night I had my 850 on its center stand, and I noticed when I turned my wheel by hand the wheel will turn about a quarter inch before the hub/sproket catches. Is this normal?

No Not Normal but likely damaging to dangerous til nipped up solid as can be again.

Maybe the chain is worn out ? More likely the cush-drive rubbers pack is old and crushed? Pull the rear wheel and inspect.

Forgive me for my ignorance, the norton thing is still new to me. What is the Cush drive? My bike was my fathers, and he rebuilt it from the ground up in the mid nineties, and the bike currently has about 6k miles since the restoration. Should those rubbers be worn out in that amount of time?

nortncom said:

Last night I had my 850 on its center stand, and I noticed when I turned my wheel by hand the wheel will turn about a quarter inch before the hub/sproket catches. Is this normal?

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Two possible causes, either the cush drive rubbers are in need of replacement as already mentioned by Torontonian, or there is backlash between the sprocket drive paddles/vanes and the drive centre slots? Some backlash between the sprocket and the wheel on Mk3s is fairly common and doesn't appear to cause any problems however 1/4" is possibly a little too much. Perhaps a check of the drive and cush would be advisable just to be sure?

nortncom said:

Forgive me for my ignorance, the norton thing is still new to me. What is the Cush drive? My bike was my fathers, and he rebuilt it from the ground up in the mid nineties, and the bike currently has about 6k miles since the restoration. Should those rubbers be worn out in that amount of time?

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Can you be certain the rubbers were changed at that time?

19 & 20
http://www.oldbritts.com/image/1975_g23.jpg

http://www.oldbritts.com/nor_mk3_75_23.html

19 06-4812 Rubber, Cush Drive, Small, Mk3
20 06-4811 Rubber, Cush Drive, Large, Mk3

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Note that it isn't necessary to disturb the chain and sprocket assembly to remove the wheel (check your workshop manual for more detailed information).

I cannot say with 100% certainty that the Cush rubbers were replaced during restoration; however, my father installed Akront wheels with polished hubs on the bike, so I'm assuming the rubbers would have been replaced during that process. I have noticed that the speedo cable runs very close to the chain when it comes off the hub. Could worn Cush rubbers cause this?

nortncom said:

I cannot say with 100% certainty that the Cush rubbers were replaced during restoration; however, my father installed Akront wheels with polished hubs on the bike, so I'm assuming the rubbers would have been replaced during that process.

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Well, whether they were replaced then or not, they may need replacing now, however the slop could still be between the sprocket paddles and slots?

nortncom said:

I have noticed that the speedo cable runs very close to the chain when it comes off the hub. Could worn Cush rubbers cause this?

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No, that's normal for the Mk3 cable.

Thanks for all the advice. I'll bite the bullet and pull the rear wheel to have a look at those rubbers. Out of curiousity, could not having enough tension on the chain cause this as well? If so, what is the correct amount of play the chain should have?

nortncom said:

Thanks for all the advice. I'll bite the bullet and pull the rear wheel to have a look at those rubbers. Out of curiousity, could not having enough tension on the chain cause this as well? If so, what is the correct amount of play the chain should have?

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It's unlikely that a slack chain will have anything to do with it.

The total chain movement should be 3/4" - 1 inch (see Mk3 manual, section C42)