2006-2009 Suzuki LT-R450 Service Manual, Page 37Get this manual
PERIODIC MAINTENANCE
Insert tool into the rear sprocket hole and adjuster hole Tense the drive chain fully by turning rear axle holder CD
Count out 21 pins (20 pitches) on the chain and measure the distance between the two pointsIf the distance exceeds the service limit, the chain must be replaced
Drive chain 20-pitch length Service limit: 319.4 mm (12.57 in)