I got mine here;
Here's the reply from them when I asked about fork springs for the 650;
thank you for your interest in the Wilbers products.
Yes, we can offer you progressive fork springs for the DL650.
The set is $ 123.00.
The rate is 6.5 / 9.5 Kg/cm
We recommend a 7.5 SEA oil with a 150 mm airspace.
It took me about 3 hours to change the springs. Part of that time was spent putting the kid to bed plus letting the fork oil settle for 30 minutes. Next time when I need to change the fork oil it should only take about 90 minutes. Overall not a bad job, if you have the right tools. Some of the tools you might not have in your toolbox are;
12mm hex socket (front axle, hard to find Craftsman doesn't make one)
24mm socket (for the fork caps)
You'll need to use the above sockets so you can use the torque wrench when you put things back together.
A few tips;
Loosen the fork cap before removing the fork. The clamping of the fork in the fork clamp will hold the fork so you can loosen the fork cap.
When putting the fork back in the clamps don’t put the fork in its final position. Stop about 6 inches short and tighten the lower fork clamp bolt temporally. This will hold the fork while you tighten the fork cap. Then loosen the lower fork clamps and put the fork in it final position. If you put the fork in its final position before tightening the fork cap you’ll find out as I did that you can’t get a socket on the fork cap because the handlebar is in the way.
Read this somewhere and it’s a great tip; take a spray bottle like this, http://science.howstuffworks.com/question673.htm
, take the bottle off and mark the plastic tube 150mm from the bottom. Fill the fork with oil, work out the air, then fully compress the fork and remove the excess oil with the sprayer, using the mark on the plastic tube as your guide for the 150mm airspace. I pumped the oil into the spray bottle for latter use.