MXA TEAM TESTED: MX1 SUSPENSION KTM 350SXF FORK AND SHOCK MODS

June 5, 2011
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WHAT IS IT?
Fork and shock mods for the 2011 KTM 350SXF from KTM specialist Dick Wilk.

WHAT’S IT COST?
$295.00 (HFP fork mods); $135.00 (fork springs and oil); $495.00 (fork leg DLC coating); $195.00 (PDS shock mods); $175.00 (shock reservoir); $75.00 (aluminum preload ring); $135.00 (shock spring and oil).

CONTACT?
www.mx1suspension.com or (916) 741-8767.


WHAT STANDS OUT?
Here’s a list of things that stand out with MX1 Suspension’s KTM 350SXF mods.

(1) Fork revalve. The stock 0.46 kg/mm fork springs are too soft, and the midstroke compression is on the fast side. Dick Wilkes of MX1 installed stiffer 0.50 springs and increased the compression damping by utilizing his High-Flow compression pistons (HFP). Oil height remained at 375cc. The goal was to hold the forks higher in their stroke, slow down the midstroke damping, and add a touch more rebound for the stiffer springs. The fork legs were DLC-coated to reduce stiction.

(2) Shock revalve. The stock KTM shock spring is a 5.4 kg/mm. That is too soft for anyone over 175 pounds. MX1 exchanged the stock spring for a stiffer 5.8 kg/mm spring. This is necessary since the WP shock flows a lot of oil and is very soft on damping (Dick Wilkes thinks that KTM overestimated the damping rate of their new linkage). MX1 upped the compression and rebound damping to more traditional rates (read “Kayaba” rates) and used a special bypass valve to help keep the rear of the bike higher in its stroke.

(3) Shock reservoir. To fight the heat of the 350SXF’s increased shaft speeds, Wilkes replaced the stock reservoir and its piston with a totally new reservoir and bladder system.

(4) Preload adjuster.
The MXA test riders hate KTM’s nylon preload ring. It is hard to work with and tends to seize up. Thankfully, MX1 offers a CNC-machined aluminum preload ring to replace the shoddy nylon one.

(5) Options.
MX1 also offers a fork rebuild in which the seals and bushings are replaced and the tubes are polished for $95 (plus parts) and only $45 if you are having the forks revalved. A shock rebuild is $125 (plus parts) and only $25 with a shock revalve.

(6) Fork performance. What a difference. As a quick fix, the MXA test crew had installed stiffer 0.50 fork springs. Although this helped, it wreaked havoc on the stock damping?which was too light in compression and rebound. MX1’s revalve provided the oil control necessary to make the forks feel more fluid and metered through the middle of the stroke. Additionally, the clicker range was increased, which allowed the same forks to be used by Pros and Novices with just a few clicks.

(7) Shock performance. Since the KTM 350SXF races in the same class and weighs within five pounds of the KTM 450SXF, it was obvious that it needed a stiffer shock spring. MX1 elected to go with a 5.8 shock spring and up the damping capabilities of the WP shock. Thanks to a larger shock reservoir, they could use a rubber bladder (which is hard to get to work in the stock reservoir). The combination of the proper shock spring, stiffer valving and more compliant reservoir allowed for a wider range of options. Most significant, the rear didn’t drop under acceleration as the stocker does.

WHAT’S THE SQUAWK? No complaints.

The stock suspension setup on the KTM 350SXF is a hot mess. It is undersprung and underdamped. MX1 fixes those problems and smoothes the action at the same time.

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