Best suggestion i've had was a chain tensioner, but its odd that its only on one side.
Quite likely to be this, it's not abnormal to have only one chain tensioner (on the drive side I presumed), as you only need just the one.
@edscoble started
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Quite likely to be this, it's not abnormal to have only one chain tensioner (on the drive side I presumed), as you only need just the one.