I'm about to buy a 2002 Yamaha big bear 400 4x4 with the selectable 4wd switch above the throttle and was wondering if these came stock with a locking front diff or not? for some reason every forum I go on has mixed opinions on this

 

easy enough to check, lift machine off the ground, lock into 4 wheel drive and see if one front tire turns without the other. If locked both front wheels will turn no matter which one makes contact. Also should be marked on selector...4wd and diff lock! Or some designation besides just 4wd...

 

Pretty sure the Big Bear didn't have diff lock. Like Kymco wrote, if it did there would be a switch for it, and an indicator on the dash. All 4WD bikes (that I know of) have a limited slip front diff if they don't have full diff lock.

Many people confuse LSD with diff lock, as a Quaif type LSD does lock up the diff if you loose traction, but bikes use a multipate clutch type LSD which slips if one front wheel starts to spin, (rather the opposite of what you want, in my opinion.)