Valve spring preload

Use a square and surface plate to check each spring for squareness in terms of clearance between end of valve spring and square. Valve springs found to exhibit a larger clearance than limit must be replaced.

Valve spring squareness limit

Inner spring: 1.6 mm (0.063 in.) 

Outer spring: 1.8 mm (0.071 in.) 

Fig 2: Checking Spring Squareness

Courtesy of SUZUKI OF AMERICA CORP.