6. CYLINDER HEAD/VALVES K-XCT 125i SPECIAL TOOLS Valve spring compressor A120E00040 TROUBLESHOOTING The poor cylinder head operation can be diagnosed by a compression test or by tracing engine Poor performance at idle speed White smoke from exhaust muffler Compression too low Worn valve stem or valve guide Damaged valve stem oil seal Compression too low Incorrect valve clearance adjustment Abnormal noise Burned or bend valves Incorrect valve clearance adjustment Incorrect valve timing Sticking valve or broken valve spring Broken valve spring Damaged or worn camshaft Poor valve and seat contact Worn cam chain tensioner Leaking cylinder head gasket Worn camshaft and rocker arm Warped or cracked cylinder head Poorly installed spark plug Compression too high Excessive carbon build-up in combustion chamber 6-3