Its doable if you skip top of the world and know where you are going. Rose Garden Hill will slow you down and is a questionable portion of the trail to do solo, you can easily gets stuck or break on that part of the trail. The majority of the trail is basically a fire road, the area near fear and loathing towers (area looks a little like Moab with some slick rock) is really easy to get lost in, even with GPS we got a little lost and went in circles for about an hour when we did it last year not a bad area to get lost in though.

Knowing where you are going is going to be the biggest issue. Find Luke (radrod57) he just did the Koko and might have a GPS file you can use.
Oh if you do this once you get down the rose garden hill I would recommend heading out to the hwy through the fisher valley I'm going to try and attach my Google earth tract for you to look at. Its to big to attach, PM me your Email and I will send it to you.
Most stuff on the www that you will find in a search is for Mountain bikes so be careful what you use as a map as it might not work.