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Hi. I recently finished restoring a 1970 T100S and thought the rear chain was shot because it was very tight in places and very slack in others (it varied between 1/2 inch of slack and 2 and 1/2 inches). So I bought a new Renold chain but when I fitted it I found it was just the same as the original one. So does this mean that the rear sprocket is worn out? A few of the teeth are a bit 'pointy' but most are fairly square.
Thanks
Tony
 

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Presumably you have the workshop manual.
In there it will state how to measure the slack.
Either on the centre-stand or with someone of similar weight sitting on the bike.
This is normally done at the point (centre) of maximum slack.
Its usual to replace both the chain and sprocket to avoid rapid wear.
Look at the gearbox driving sprocket as well.
 

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half and inch to two and a half sound like you've room to shift the chain at least one link onwards? Try that and see if the imbalance equals out.
 

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See if the rear sprocket is always in the same position,when the chain gets tight.If so,it's not running central and it has a high and low spot.
You can get a similar effect from the gearbox sprocket.

The easiest fix could be to just replace one or both sprockets,and hope the new ones are made more accurately.Measure before you buy could be a good idea.They usually have some runout,but I wouldn't like any more than 0.010".
 

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Hi. I recently finished restoring a 1970 T100S and thought the rear chain was shot because it was very tight in places and very slack in others (it varied between 1/2 inch of slack and 2 and 1/2 inches). So I bought a new Renold chain but when I fitted it I found it was just the same as the original one. So does this mean that the rear sprocket is worn out? A few of the teeth are a bit 'pointy' but most are fairly square.
Thanks
Tony
The rear sprocket sounds like it needs replacing, if the teeth have started to take on a very pointed profile but some haven't there is a good chance that the concentricity/p.c.d. will be affected so tight spots can occur; Assuming the other spkts are OK as you've restored the bike.
 
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