1981-1984 Official Honda ATC250R Shop Manual, Page 21Get this manual
ATC 250R
MAINTENANCE
DRIVE CHAIN
INSPECTION
Shift the transmission into neutralMeasure the drive chain slack midway between the sprocketsCHAIN SLACK: 10-20mm (38-34 in)
LOCK NUT
ADJUSTER
DRIVE CHAIN ADJUSTMENT
To adjust the drive chain, remove the cotter pin from the swi ng arm pivot bolt, and loosen the pivot bolt nutLoosen the drive chain adjuster lock nuts and turn the adjusting boltsCAUTION: