strange rattle!!!

[tomzxr400]

hi all was lookin at my mates zxr400 with him last week as he was complaining of a loud rattle it sounds like top end thought somethin might be loose so took tank and air box off and it still does it only does it though between 3 and 4k revs only when the bike is warm in our out of gear with the clutch pulled in or out and when speedin up or slowin down
i know his shims want doin cause can hear them but there constant was thinkin it could be cam chain cause its done 18k but would it not be constant??? any ideas would be a help

[Northern ANdy]

sounds more like something is loose and hitting its resonant frequency between 3000 and 4000 rpm. Check brackets and what not is my advice for now.

[tomzxr400]

yer thats what i thought so i took tank and air box off and it was still there not much left to be loose coils were tight carbs are on rubber so cant be them not much else it could be have to have another look tomoz he wants me to do his timming chain anyway as i am gona take the engine out to re shim it in winter well novemer ish cant say winter any more cause its shite all year now!!!