I'm putting on a SCOTTS stabilizer because I already own one. It has not let me down over the years- so I'm going to mount it up to the 640.
Unfortunately, you have to do a fair amount of modification to the STOCK triple clamp in order to make it fit. The other option is to buy a setup from SCOTT's that is addresses all the clearance issues. This includes a new top triple clamp.
I went for the SUB MOUNT.
Since I had the forks pulled off for maintenance, it was really easy to take the top triple clamp off. Make sure you first secure the LOWER triple clamp to the frame. Otherwise, when you loosen the head bolt, the whole assemble will hit the floor.
Once you have unbolteded the top triple clamp, you need to disconnect the ignition- just follow the plug to the right side of the shroud. Undo the cable guide thingey as well. Now you are free.
Flip it over and- using a dremel tool, cut a slot in both of the bolt heads that hold the ignition assembly onto the stock triple clamp.
Using a GOOD screwdriver, get it out ASAP. The heat from the grinding helps loosen the loctite.
Next you need to cut down the steering stop. I used a dremel to get the line cut, and then finished with a hacksaw. The idea is to give the FRAME CLAMP enough room to seat on the steering stem.
Following the directions from SCOTT's is very easy. Ultimately, you want the frame clamp to seat onto the steering tube so it sits flush with the bearing surface. Mine fit right on, no need for any filing etc.
Next step is to slide the fork tubes back into place and line everything up. Since I was sent the WRONG length fork springs, I'll have to wait until next week to perform this.
This is a VERY easy install. Do not get flustered by the fact that you have to do some cutting and grinding.