I posted this earlier on a Swingarm Boot post but thought I would do a specific post on it here.
Take the time to remove your Rear Diff skid plate and check to see if your gray rubber plug is there between the skid plate thread mounting bosses is there. Mine was left out from the factory.

 

you dont happen to have a pic do you? i think mine is missing it also but im not sure. can you buy a plug for it or can you just squirt some silicon up in there?

 

The plug is the same as the ones on the side. P/N 92066-1534. I would avoid the adheasive unless you put a very light coat on the plug at install.

 

I've got to pull my swingarm off; discovered a missing plug on the side and don't know how long it's been gone.[img]i/expressions/face-icon-small-blush.gif[/img]

 

I feel for you on the pulling of the swingarm. If you have not done this yet let me fill you in.
After disconnecting the shock at the lower conecting point and the break cables, get a long handled 1/2 inch breaker bar and a cheater. Don't use a ratchet unless you don't care about it.
Get some of that permanent white marker and mark your threads and hexes on both sides.
You will need a 30mm socket.
Mine pulled hard on the nut side all the way out. They have some kind of white-ish thread locking compound that is a real bear.
Fun stuff.
I did mine alone and if I have to go in again I may try and leave the tires on for the install.