YOu don't have to split the cases, just remove the foot peg and clutch cover. YOu'll find you problem in there somewhere. You might have a new clutch cover gasket on hand just in case the old one tears. The idler gear is behind the clutch basket. It is the gear that the kick starter gear engages. If you can wobble that gear easily, the clip and washer are gone, which you will most likely find somewhere in the clutch cover. You'll have to order a new clip and/or washer, and maybe a new bushing for that gear, BUT that may not be the issue.
Be sure you have a good big phillips screw bit or even an impact screwdriver (the kind that you hit with a hammer) as those clutch cover bolts strip very easily. While your at it, you could be allen head replacement bolts for cheap from rockymountain atv, or wherever.