Measure the outer diameter of camshaft journal with a micrometer.
Standard:
No. 1: 27.935 - 27.955 mm (1.0998 - 1.1006 in)
No. 2, 3, 4, 5: 23.435 - 23.455 mm (0.9226 - 0.9234 in)
Courtesy of SUZUKI OF AMERICA CORP.