2003 Suzuki LT-Z400 Factory Service Manual, Page 271Get this manual
SERVICING INFORMATION
Complaint Engine is noisy
Symptom and possible causes Excessive valve chatter 1Excessive tappet clearance2Weak or broken valve spring3Worn camshaft4Worn or burnt camshaft journalNoise seems to come from the piston 1Worn piston2Worn cylinder3Carbon buildup in combustion chamber4Worn piston pin or piston pin bore5Worn piston ring or ring grooveNoise seems to come from the cam chain 1Stretched cam chainAdjustReplaceReplaceReplaceReplaceReplaceCleanReplaceReplace