I thought I could find that specification on rear suspension travel, but I don't see it in the sales brochure, Owner's Manual, or Workshop Manual.
The front is 120mm. I have an internet reference that says 128mm, but I just don't see it anywhere in the official literature.
The Workshop manual lists the free length of the spring at 165mm to be preloaded from 8mm -14mm. That doesn't seem like much of a range. Before I switched to the Öhlins, I set my Sachs-Boge spring to 18mm preload which is over-compressed and beyond the recommendation.
You are more likely better with the correct spring for your needs!