The 650's have old fashioned damper rod forks so the damping is not very sophisticated, especially compared to a GSA. Some find that changing the preload, springs and/or oil good enough. However, one can fit a valve to simulate a cartridge such as Gold Valve Emulators or Imitators. Another solution (but more expensive) is to replace the damper rods with set of cartridges either from a DL1k or after market item. There are threads on here somewhere about these.
I've just about finished doing a conversion with a set of Traxxion Dynamics cartridges I had from another bike of similar weight and style but have not had it on the road yet. After market cartridges often have the benefit of adjustable compression and rebound damping as well.
