Do not even dream of fitting new extra links to a chain that has been used.
I have some sad news for you.
You should never mix old sprockets and chains with new or second hand ones.
They marry for life, and do not take kindly to another partnership.
A new sprocket will quickly wear/stretch or break an old chain.
A new chain on an old sprocket can be completly stuffed in a few miles.
Rule of thumb, always replace the whole set, chain, front and back sprockets.
The 8 links of new chain are going to play havoc with the sprockets, and will be taking a fair amount of extra strain as they try to ramp on the old sprockets.
If you fit new chain to an already used one, make sure you have the case saver in place before you ride, you may well get it tested.
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