Sorry...my bad. The screws on my Bonneville are dished out, a nickel is what fits.... But you can use a nickel on the Vulcan too...it's the right thickness to match the grooves.Hmm, mine aren't dished out. Wish they were! A quarter slips right out.
x2 A coin does the job perfectly. My 2000 has the dished out cross groves as mentioned and there is nothing in my original tool kit that seems to work. Using a washer is great and can be carried on the key ring so it is aways handy rather than stuffed in the rear tool box where it will be lost just before you need it out on the road.Actually the screw is designed to be removed with a coin.
(Can't remember if it's a quarter or a nickel or what)... but it's dished out for something round. I don't remember there being a specific tool in the stock tool kit for it.
I found the perfect sized washer that fit it and used that....but yes, a big ass screwdriver will work too, just don't over tighten it.