If you go here Browse
build your quad and then look under the front drive section. The bolt numbered 15 should be the one to loosen for your front chain adjustment.
I know the "VOICES" aren't real but they have some great ideas.
1999 Sport 400 2x4
Complete rebuild w/Wiseco piston by Todd Kerby, Comet clutch, Swamplites front & rear, 03 Predator Rear Hubs,
ITP Pro Baja Wheels (4x156 front & rear), DG Front Bumper, Fuj Rear Grab Bars and RZR Belt