How do i know when my belt needs replacing?

 

Assuming that an 02 600 Grizz uses the same drive belt as an 03 660 the measurement specs should be correct.

1- Remove the v-belt from the sheaves and inspect the inner side ( side with the teeth ) for cracks/wear/scaling/chipping replace if something does not look right.

2- Measure the width of the v-belt with a micrometer. A new belt should be 33.2 mm (1.31 in)
The wear limit is 29.9 mm (1.18 in) If it is worn beyond that replace the belt.
The measurement is taken at the outermost angles of the belt.

While you are there you should clean out and regrease the primary and secondary sheaves.
You will need a manual/ or service cd and tools to do the job. Post back on the progress or if you have questions.