Engine sounding a little rattly

[mtread]

..... and just to elaborate, the camchain has an automated tensioner that adjusts itself (supposedly) when the chain gets slack. They tend to rattle just before the tensioner moves on a cog and takes up the slack. It's been suggested you can force the tensioner up by rolling the bike backwards in gear (but I've never tried it). You shouldn't usually need to replace the camchain after only 20k.
The other Fazer rattle is the clutch. Does it quieten when you pull the clutch in ? If so, nothing to worry about, they all do that.