Any suggestions on how to get to the rear shock preload adjustment? It's a little soft for my weight, but man it's a pain to get to. Is there a special tool or something ?

 

I use a long spaner wrench from the left side, in front of the rear fender. it is a slow process at best. you dont get much of a turn. but it works.

 

I used a long flat screwdriver & hammer to break the lock nut free, put it on a stand to get the wheels off the ground and adjust it. Then used the screwdriver to lock the nut back in place.

 

If you take the weight off of it, but not all of it, then once you get the lock ring cracked like JMAC described, you can spin the spring by hand, and this will catch the adjusting ring and turn it as well.

The hardest part is finding the neutral weight. no weight on the shock, but no pull either.
Good luck