Hoolander2 - I used a 9mm open end wrench for the locknuts - about 8" long - fairly thin. It got right in to the locknuts. First time around I used needle nose pliers to adjust - didn't work too well, and I didn't get them dialed in. So, I ordered the adjustment tool from my local dealer. I gave them the Kymco part number, they ordered it and were told the number had changed. When I got the tool it wouldn't fit all the way in through the guide holes except for one valve ! It had a knurled round handle and about a 2 1/2 - 3" extension to get to the valve adjust screw. Nice tool, didn't work. I was lucky, the knurled handle was threaded onto the extension part so I unscrewed it and threaded it onto a wooden dowel to add some length. It worked out well. $ 19.95 tool from the dealer ! But it sure made the adjustment a lot easier and better than the pliers.