Since they're off a 680 Rincon, the rears won't work because the 680 Rincon has IRS and the offset will be different. They will sit in too far and probably rub the muffler or something. It would be like putting the front rims on the rear of your 300. You might be able to put wheel spacers on the rear and make them work.
Is that a 600 Grizzly in your avatar?
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.