A tip for you.
First off the adjuster bolt (as shown in the pic on the last post) is actually the adjuster lock bolt.
First loosed the M8 nut, couple of turns is enough. Start the motor and let idle at 1200 rpm, then back off the lock bolt (use a 10mm socket with extension bar) about half a turn. you should notice a change in the sound of the cam chain. "nip up the lock bolt. the reason so many motors have the bolt broken off is through over tightening. lock the m8 nut. Job done.
Now if when the lock bolt was loosened, there was no change or the rattling got worse.
Above the lock bolt there is a plug, remove this plug, don't loose the sealing washer. back off the M8 nut again, start the motor. have a long thin screwdriver handy that you can insert into the hole that the plug came out off, back off the lockbolt as before and insert the screw driver into the hole, apply some light pressure to push the plunger down (if it won't move or you don't hear the chain get quieter then the cam chain horseshoe adjuster is seized from the chain grinding into it). If the chain does get quieter then keep the pressure on the screw driver and NIP up the lockbolt.
Hope I've explained this OK.
Kevin