MOTOCROSS ACTION PRODUCT TEST: MX1 SUSPENSION YAMAHA YZ450F FORK/SHOCK REVALVE

WHAT IS IT?
A first-class fix for the front and rear Kayaba SSS suspension components on 2010 YZ450Fs.

WHAT’S IT DO? MXA‘s first step when testing suspension is to carefully set the ride height. We then put the clickers in the recommended positions and start riding. We work with the forks first, and once we are happy with the forks, we start on the shock. (Of course, we always have to return to the forks again?because changing one end changes the other.) We never make fork and shock changes at the same time. Testing is always backed up by racing?which is the true test of race suspension. Often what works at the test track on Thursday doesn’t work on the racetrack on Sunday. We spent two months testing MX1 Suspension on our 2010 YZ450F. This is what we discovered.

WHAT STANDS OUT? Here’s a list of things that stand out with MX1 Suspension’s YZ450F setup.

(1) Forks. The biggest problem with the YZ450F forks is that they are out of balance with the stiffer rear. Thus, if you can only afford to fix one end, work on the shock. If you would like to get both ends super-tuned, however, here is what MX1 Suspension did to our YZ450F forks. First, they installed stiffer 0.49 kg/mm fork springs. The stiffer spring rate held the forks higher in their stroke, but, most importantly, it allowed MX1 to change the compression and mid-valve to a much plusher setting. This allowed the forks to flow better through their travel, while depending on the spring for bottoming control. Unlike other Kayaba forks, the YZ450F forks do not have a “free bleed” hole in the piston, which means most previous Kayaba fork knowledge cannot be applied to the YZ450F. MX1 tried multiple rebound settings to compensate for the lack of free bleed, eventually finding the right combination to match the springs. Every MXA test rider loved the forks. One or two clicks in either direction made a noticeable difference in feel.

(2) Shock. We stayed with the stock shock spring. It is well-suited to the target weight of the typical YZ450F rider. The main goal was to get plusher compression without introducing blow-through. How can you make the shock feel softer without having it bottom? MX1’s answer was to reduce the size of the shock’s “free bleed adjuster passage.” This mod was combined with lighter compression damping to make the shock move more freely in the first two-thirds of the stroke. In addition, an old school air bleed circuit was added to ensure air-free performance. In MXA‘s opinion, the MX1 shock would have worked well with the stock forks because it would have lessened the stinkbug stance and allowed the chassis to ride level. But the combination of front and rear MX1 mods was pretty sweet.

(3) Fork adjusters. MX1 built us a set of special compression adjusters that could be clicked by hand. This made testing and setup much easier than trying to wedge a screwdriver into the Kayaba slot. Unfortunately, making the KTM-style knobs is a complicated process, and the cost is $145.00.

WHAT’S THE SQUAWK? We loved the adjustable compression knobs, but broke them twice.

We’d rate these as a five-star shock and a four-star fork (because the stock forks are very good on their own). MX1 has found the key to suspension that not only handles big loads, but is plush at the same time. That’s a wonderful combination.