Re: My chain is saggy
"Grinding the rear sprocket"
Not quite sure what you mean here. If the chain and sprockets are aligned there should be no grinding.
As for getting the proper tension; you might have to remove a link. In the case of roller chain that is in reality two links. The tensioner bracket can be moved forward or toward the rear to get the tension right but if there isn't enough adjustment to get that 1/2 to 3/4" slack I mentioned then you'll need to shorten the chain.
If you don't have the tools or experience with shortening chains either a bicycle or a motorcycle shop should be able to help you. Tools are available, called 'chain breakers'.
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