By turning the engine backwards it's crates a little bit of slack (I mean little) this slack if it's large enough, will allow the tensioner to click up to the next notch. We're talking mm here and it's not always successful, in which case you need to remove and reset the tensioner, if that doesn't work replace it as the tooth it now needs to engage with is worn/damaged.
If that doesn't work it's highly likely the chain is now worn and will need to be replaced. All that said Fazers have an extremely reliable cam chain mechanism, often the noise owners think is cam chain isn't, it's out of balance carbs or clutch rattle.