no progressive springs, but two springs of different rates which have similar effect.
So technically speaking the early S had progressive springs and the later one did not???
No.
A
progressive spring is a
single spring that is built with variable rates of compression along its length. There are two types. One is more commonly known as the
progressive spring and the other is known as a dual rate spring. In either you will notice how the coil space changes along its length—more gradually in the
progressive example.
Progressive
Dual rate progressive
In the early K75S with Sport fork there were
two main compression springs and two secondary compression in both legs. One leg had different valving to control rebound. I don't know whether one of the two main springs had differing compression rate from the other because I haven't disassembled one but if member
K1300S indicates they do, that's enough to convince me they do.
Sport fork
In the later Showa fork, there was
one main compression spring in each fork leg. I bought a '95 K75 that had approximately 25K miles on the clock. When I dismantled the fork tubes to inspect their components, what I saw is illustrated below. The main spring looked like the spring above labeled
Progressive. I don't know if the original owner had installed this but he seemed savvy regarding motorcycle performance.
