This is the issue with the forks:
That is the cartridge tube. When BMW says non adjustable they mean it, the ends are crimped.
KLR's have damping rod forks. A rod/plunger forces oil through fixed holes in cartridge tube. low tech but easily modified. Thinner/thicker oil viscosity effect how fast the oil flows through the tube. You have cheap options like cartridge emulators.
The 800 has a compression valve crimped into the bottom. It uses washers for the oil to pass through. The oil flows around the washer and/or bends them. The viscosity benefit is limited. Too light an oil and it gets past the washer easily. Too heavy a viscosity and it will force the washers to bend too much/ too quick. The proper fix is change the stack of washers.
Usually changing springs will create a need to change the resistance in the compression valve. You can't do that with these.
This is a cheap solution that causes the owners to spend more than necessary to fix. At least Triumph and KTM have better suspension guru's
or accountants are not part of the design team.
My first ride of substance was Death/Saline Valley. I survived it also, though not much fun. A dinged rim (22psi) and a tank slapper between Race track and Lippincott. I am chasing an ADV rider on a Wee Strom and losing.
Not a lot of options in 2009. I did the springs/oil and later the first available cartridge tube. I fixed the abrupt throttle and moved the COG forward a little with suspension adjustments. That made a significant change in this bike.
I now have a stabilizer, but it was the last modification and not a requirement.
Yes I can ride it faster, but it is also easier to ride. Mine is a very stable bike.