Does anybody have any good suggestions for a tool to adjust the fork pre-load? Preferably something better than a pair of pliers but without spending a lot coin.

10mm open end wrench?

Rick

+1 

When I took off my handlebars I used the 10mm wrench. It worked okay but if I want to adjust it with everything together it seems like it would be a pain.

I'm guessing you have risers installed.  Without the risers, a 10mm wrench works just fine.  With risers, like I have, I still use a 10mm wrench, but have to carefully count the turns I make, since I can't see the lines on the sides of the adjusters.

I made a tool out of 1/2" copper tubing and fittings.  I used a "t" fitting for the handle attached to an 8 inch section.  I notched out a cap on the end of the 8 inch section approximating a 10mm wrench.