2006-2009 Suzuki LT-Z50 QuadSport ATV Factory Service Manual, Page 57Get this manual
VALVE SPRING The force of the coil spring keeps the valve seat tightWeakened spring results in reduced engine power output, and often account for the chattering noise coming from the valve mechanism Check the valve springs for proper strength by measuring their free length and also by the force required to compress them If the spring length is less than the service limit, or if the force required to compress the spring does not fall within the range specified, replace the valve springValve spring free length (INEX): Service Limit: 22.8 mm (0.90 in) Valve spring tension (INEX): 36.5 41.9 (3.7 4.3 kgf, 8.2 9.5 lbs) at length 15.0 mm (0.59 in) 09900-20102: Vernier calipers