MXA PRODUCT TEST: PRO CIRCUIT KX450F LINKAGE AND REVALVE
WHAT IS IT? An aftermarket shock linkage and shock revalve for the 2006 Kawasaki KX450F that alters the rising rate, lowers the seat height and mitigates bottoming.
WHAT’S IT COST? $184.95 (linkage), $149.95 (shock revalve) and $7.95 (shock oil)(951) 738-8050.
WHAT’S IT DO? Every MXA test rider has concerns about the rear suspension of the 2006 KX450F. In stock trim, it wallows (sways under acceleration), bottoms (so hard that it can break the rear fender) and pogos (bounces up and down on undulating terrain). Pro Circuit has a two-step plan to calm the rear of the KX450F.
Step one: A new set of strut arms were CNC-machined to lower the seat height and rotate the stock bell-crank into a firmer portion of its progression.
Step two: A totally revalved shock with vastly increased rebound damping (something the stock KX shock sorely needs) and a more progressive rate change to keep the shock from bottoming.
With the release of the all-new 2006 Kawasaki KX450F, Pro Circuit went to the mat to improve the KX450F’s questionable suspension.
WHAT STANDS OUT? Here’s a list of things that stand out with the Pro Circuit 2006 KX450F linkage and shock revalve.
(1) Performance. In the world of shock linkages, Pro Circuit knows what it is talking about. They make linkage systems for the KX125, KX250, KX250F and KX450F. The dog-bone used on the KX450F is a cheap and simple way to mitigate some of the KX450F’s worst flaws (and Stewart uses it). Pro Circuit’s linkage changes the leverage ratio to hold the KX450F shock higher in its stroke longer. In motion, it feels one spring rate stiffer throughout the stroke. By shortening the dog-bone from 132.5mm to 131.5mm, the Pro Circuit link lowers the rear of the KX by 7mm.
(2) Dual-action. Not a single MXA test rider liked the way the stock KX450F rear suspension felt. Initially, we tried a stiffer 5.7 kg/mm shock spring. This improved compression and lessened the wallow, but aggravated the rebound and didn’t help bottoming control. Unfortunately, the Pro Circuit linkage only rotates the bell-crank enough to affect the first two-thirds (225mm) of the shock’s travel. Even with the link, the KX450F will still be busy from mid-stroke on. The final solution must be found in the shock’s valving. To that end, Pro Circuit’s Bones Bacon revalved our shock to add needed rebound and stop the spike at the end of the stroke.
(3) Installation. The CNC-machined Pro Circuit linkage comes with the bearings and seals installed. All you have to do is replace the stocker.
WHAT’S THE SQUAWK? Kawasaki’s engineers should take a look at what their race teams run so that the consumer doesn’t have to make a rising rate change.