Wow, the stock shock has a rebound but not a compression?
Wouldn't the compression be the one we'd want more?
I'm no expert, I guess rebound might be important and many a well tuned spring wouldn't need as much compression adjustment, but seems like if you're going to design a shock, why not have both?
Motorcycles are very much so Rebound dominant vehicles in terms of the relationship of required Rebound Damping Force as compared to Compression Damping Force.
The best simple evidence of that is the typical Damping Force Curves for a shock, where a 3X relationship in force can easily exist at a stroke velocity of 4 inches per second.
So if you want to build a cheap shock, but give someone a single screw to play with - Rebound it is, as it has more effect.
A very squat prone machine, the 919 being an excellent example, can definitely use much more Low Speed Compression damping force, and more spring rate, when the bike is in the squat mode.
But Mr. Honda didn't envision that, and figured no one would pay for it, let alone the better idea of using a linked suspension and higher swing arm pivot pin height.
Ultimately, if you can only have one damping force adjustment, Rebound is chosen every time.
Rebound is more important than Compression for a motorcycle.
Spring rate alone can not replace the need for some low speed compression damping force, and rest assured, the stock shock has some.
Generally speaking, spring rates are selected exclusive of the damping force curves.
It's more a case of have damping force characteristics that are suited for the spring force energy and the chassis inputs.
Price and Cost conspired to keep us from getting really good two or three way adjustable dampers on our 919s. (Hi speed compression adjustment is a track only need)
Too much rebound will put you on your head.
Too much compression will give you a harsh buckboard ride.
Far better to be able to tune the one that will put you on your head.