I've posted pics in this thread of the stock setup. It only has damping on the RHS. Although I was warned about the "peening" by another suspension guy, Racetech was able to replace the valving (w/shim stack) by machining the mounting post. In other words, they were indeed able to "put it all back together." Not a job for the average shop, though. And my sag is only 30 mm, 40 sounds like too much.
Increasing the spring rate will require more rebound damping and less compression. You won't get that with the stock valving no matter what you do with the oil viscosity or level.
41mm is 27% of total travel, provided the entire stroke is available. General rule of thumb on a street bike is 25-33%. at 41mm, the available stroke is around 3.4 inches factoring that even under maximum braking yesterday, I was not able to access the bottom 1" of travel (likely due to oil level). What we don't want is a fork which tops-out quickly under acceleration, as it can lead to tank-slappers when powering out of corners, and can cause ride quality issues when the road surface falls away quickly (read: speed bumps, pot holes, etc), depending on other factors such as the top-out spring length and rate, and given how much preload is said to be installed, the top-out spring is likely to be very short and stiff.
On a typical street sportbike, 30-40mm is the target range. For reference, I run 32mm of front sag on my RSV4, for both street and track use, and that's with a 1.0kg/mm front spring, and a 140mm oil level, on a fork with 126mm of total travel (with 25mm GP Suspension) cartridges. One difference though, is that I can actually use the complete stroke on the RSV4 less maybe 5mm, but the only time it occurs is braking from 170mph on the track with a hot race tire on the front.
On to the bigger topic - the issue is not 35mm, 40mm, 45mm of sag, because functionally the fork will behave the same at any of those points in the stroke, and we're only worried about geometry. Thankfully, the Hyper has a decent base trail value and isn't on a razor's edge in terms of setup.
My primary concern is oil level. I want access to the entire stroke, less maybe 5mm. Additionally, I do not want a fork which is so progressive at the bottom of the stroke as to overwhelm the rebound damping of the fork, as it affects feel under heavy braking.
I have a lot more thoughts on the topic and the Hyper, but I'll wait until I've had more time to experiment with the setting.
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