Knock from primary side when kickstart engaged

[toastyhamster]

Finally got my kickstart together (not easy getting that clip over the spring) and fitted it to the engine. When taking up the slack with my foot there's a knock from the primary side - closer inspection revelas it's the chain tensioner hitting the outer cover as the slack on the chain is taken up. Is this normal or does it mean the spring on the tensioner is too weak and needs renewing?