Checking engine mount bolts
Engine mount bolts are one thing that will loosen up with time and vibration. This can happen in as little as 7500 miles, so it would be a good idea to check the torque a couple times a year, or at least as part of the winterization process. You should also check the other fasteners periodically, too.
There are only 3 mount bolts, and they all have a torque value of 24 ft-lbs and use a 14mm socket. There are two at the rear and one at the front of the engine. Use red (high-strength) thread locking compound on these bolts to prevent them from loosening again so quickly, although since you'll probably be pulling the front one when you adjust the valves, just use blue Loctite on that one.
The rear two bolts both have nuts on them. The nuts are located on the right side of the bike.
If the bolt is not tightening, you may need another socket to hold the other end which, conveniently enough, is on the left side.
Left picture is the top bolt head; bottom one at right.
If you need to replace one of the nuts, they are Kawasaki part #92015-1180; NUT,FLANGED,10MM. Should you be looking for one at your local hardware store, you need size M10-1.25, which is 10mm with a pitch of 1.25.
The front bolt does not have a nut; it screws directly into the front bracket. It is accessible from the left front side of the bike. You can fit a 14mm socket into the fairing vent, but you will need a ~6" extension to get a wrench on it.