Zou kunnen; ik heb hier de dikke meertalige Jawa 350/638-639-640, uitgave van 1992, blz. 112:
'The chain is tensioned correctly if, after releasing the top rubber chainguard, the chain can be lifted with the finger at least 3 centimeters. This slack ensures that the chain will never be fully stretched during the ride due to the up and down swinging arm, which otherwise would result in shortening of the chain service life and damaging of the bearing of the secondary sprocket in the gearbox.'
Dezelfde tekst staat ook in de uitgave van (alleen Engels) 2004. Opvallend dat er zelfs staat 'ten minste 3 centimeter'. Wel met 'de vinger'!
Dit gaat over de secundaire ketting...