2003 Polaris ATV Trail Boss 330 Factory Service Manual, Page 42Get this manual
MAINTENANCE After inspection, again slowly move the ATV forward until all the chain slack is on the top side of the chain and inspect the deflectionRepeat this procedure several times to check different spots on the chainThe chain is correctly adjusted when the tightest portion of the chain itself has approximately 38 in (10 mm) of deflectionIt's common characteristic of any chain to have one or more tight spots in the chainTherefore, it is extremely important to check chain deflection in several areas of the chain to ensure deflection is correct at the tightest point
Loosen Eccentric clamp bolts (Step 2)
Loosen (2) caliper mounting bracket bolts (Step 3)