Lube all the cables and change the lube in the differentials (85W90). And check the muffler bearings. They were quite a problem on the Big Bears.

Plug $5

Oil (3.5 qts. @ 3.00/qt.) $12

Air filter (spray cleaner and reoiler kit for the foam sleeve) $15.00

Oil (for cables, you probobly have around) $0

Bottle of gear lube (85W90) $5

Should be doing it ATLEAST once a year, regardless of time used and more like 2X.