2003 Suzuki LT-Z400 Factory Service Manual, Page 78Get this manual
GROOVE fork plays an important role in the of the shifting processMeasure the fork clearance in the groove of its respecthe thickness gaugetive gear If the clearance exceeds specification, the fork, its or both,
0990020803: Thickness gauge 09900-20101; Vernier calipers clearance Service Limit: 0.50 mm (0.020 in)