Suzuki drz 400E Service Manual page 71

VALVE SEAT SEALING CONDITION INSPECTION
With the valve and valve spring assembled, pour a small quan-
tity of gasoline into the intake or exhaust port.
Check that no gasoline leaks through the valve seat. If leakage
is found, correct the sealing surface.
Gasoline is highly flammable and explosive.
Keep heat, sparks, and flames away from gasoline.
VALVE SPRING
The force of the coil spring keeps the valve seat tight. A weak-
ened spring results in reduced engine power output and accounts
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 re-
quired to compress the valve spring is not within specification,
replace both the inner and outer springs as a set.
Valve spring free length (IN & EX)
Service Limit:
INNER: 32.6 mm (1.28 in)
OUTER:36.3 mm (1.43 in)
Valve spring tension (IN & EX)
Standard:
INNER: 5.6 – 6.4 kgf/27.4 mm (12.3 – 14.1 lbs/1.08 in)
OUTER:12.6 – 14.5 kgf/30.9 mm (27.7 – 32.0 lbs/1.22 in)
ENGINE 3-29