2006-2009 Suzuki LT-R450 Service Manual, Page 80Get this manual
VALVE SPRING The force of the coil spring keeps the valve seat tightWeakened spring results in reduced engine power output, and often accounts for the chattering noise coming from the valve mechanismCheck the valve spring for proper strength by measuring its free length and also by the force required to compress itIf 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 spring
Valve spring free length: Service limit: (IN 34.0 mm (1.34 in) (EX 33.3 mm (1.31 in)
IN Approx 119137 (11.913.7 kg!) EXApprox 78.5 (7.85 kg!)
IN 30.9 mm (1 .22 in) EX 30.9 mm (1.22 in)