SHOWA forks have long been an excellent choice for motorcycle suspension, and recently SHOWA introduced the SHOWA SFF (Separate Function Fork) which makes more exact tuning of the front suspension on the 2011, 2012 & 2013 Kawasaki KX250F (and for 2013, the Suzuki RMZ250 & RMZ450's) a whole lot easier than previous models as the SHOWA SFF fork allows external adjustment of the front suspension's spring preload and resultant sag through the use of the external preload adjuster located at the top of the right fork leg.
Although the idea of separating the damping functions in a fork is nothing new as Marzocchi had implemented this design in 1993 with their conventional style 45mm "Magnum" forks.
Similarly to the previous Zoke's, (although greatly advanced in valving technology) the Showa SFF fork houses the damping in one leg, while the other houses the main spring, hence the name Separate Function Fork (S.F.F).
We're not here to provide any test data or opinions of the SFF over other dual chamber style forks but we can say there are obvious benefits to this fork over previous models from it's simplicity, to the fact that the SHOWA SFF setup is approximately 1.5 Lbs lighter than previous model forks which is achieved with only one leg handling the damping, while the other is responsible for housing the spring.
The left leg of a SHOWA SFF is essentially nothing more than a Twin Chamber fork (minus a spring) where you'd normally find an external low speed compression damping adjuster at the top of the left fork leg, with a low speed rebound adjuster positioned at the bottom of the LH fork leg in just the same manner as previous versions of the SHOWA TC (Twin Chamber) fork.
Considering external adjustments and tunability of a fork leg, there's not much difference between the left leg of a SHOWA SFF and a previous Twin Chamber fork.
Anytime you're measuring or adjusting the sag it's best to get both the front and rear balanced together (yes, the amount the front fork's sag under weight is adjustable) although with conventional, cartridge or twin chamber forks, adjusting the front sag was never possible without disassembling the forks to add washers or spacers under the spring so as to affect the fork preload. Needless to say, for most amateur racers or riders, adjusting the front sag is something that rarely, if ever got messed with.
With the SHOWA SFF, external adjustments to the forks are no longer limited to compression damping, rebound damping and fork height, now the fork's spring preload, ride height and sag can be fine tuned via the external preload adjuster located on the top of the RH fork leg.
The amount the front of the bike sags under weight or dives under braking is adjustable through the use of replacement spring(s) and / or preload adjustments although to add or remove spring preload in most forks, doing so requires disassembly of the forks so as to enable placement of washers, shims and spacers under the fork springs.
Fortunately on a SHOWA SFF, the spring preload is externally adjustable (to a point, at which point a replacement spring will be necessary to maintain the proper balance).
Don't Forget that 6 clicks of the knob equates to 1mm of PRELOAD, NOT actual sag.
As with any adjustment of the motorcycle in a quest for better performance, it's important to constantly test different setups from tracks or riding spots, although once an ideal ride height setting is achieved, and the motorcycle feels well balanced & mannered, measure the compressed distance again and record this in one of our basic setup logs, this way you can refer to this for later reference when returning to a specific track or riding spot.
Wondering If We Cover More of Your Dirt Bike Interests?
Find Out Right Now.