2016 KTM 350SX-F: Suspension Mods

After getting wind of just how much KTM’s 350SX-F had improved for 2016, Transmoto’s Ben Foster traded his left nut to ensure one found a home in his garage for the next six months. Here, Fozzie offers up an insight into the suspension work he’s had done, that has quickly translated into noticeable gains in performance and rideability. 

While the 350’s chassis has one of the more refined set-ups I’ve ridden, the suspension – in particular, WP’s 4CS fork – was quite a way off the mark from what I was chasing. After KTM’s international launch for their 2016 models (featured in issue #51), Transmoto Editor Andy Wigan and KTM test pilot Mike Sleeter both singled out the 2016-spec 4CS fork being particularly forgiving. And, as Sleeter said, the new settings were aimed more at the average guy than Pro racers, who’d change the set-up to suit them anyway. Well, the 4CS fork is soft – probably the softest fork we’ve tested on a production MX bike for some years. I found they blew through the initial part of the stroke very quickly – especially on the faster and rougher terrain – which left them operating in a lower, harsher portion of the stroke. And that left me struggling for front-end grip and predictability.

The shock, on the other hand, worked pretty well, even with my 86kg weight – although this may have been somewhat masked by the lack of performance from the fork. So, to find the balance I was looking for, I spent some time with Factory Spec Suspension’s Ken Wheeler. Kenny’s an ex-KTM race team technician, a regular rider himself and knows his way around a valve stack better than he does a keyboard, so he was the perfect man for the job. The outcome so far has been a far better balanced, more predictable and faster bike. As a result, my lap times have come down, my time on track has gone up, and the overall feel is much more confidence-inspiring and enjoyable.

So, what mods did Factory Spec Suspension perform to improve the handling so markedly? Ken Wheeler explains:

“We were lucky in that both the standard fork and shock springs were fine for Ben’s 86kg weight, but the majority of the work needed was in the front-end on the 350. There’s not a lot of valving there that actually holds the 2016-spec WP 4CS fork up in its stroke for a faster rider. The biggest change I made was to the mid-speed valving. They’ve got such a small piston that you need to get the damping working straight up to help control the compression stroke of the fork. The end result has been the fork riding higher in the stroke, without creating a harsh feel to achieve this. It’s firmer, but also a more controlled and smoother ride. It’s almost the opposite of the standard set-up, which is really soft initially and rides low, yet actually feels harsh.

“The shock isn’t as bad, but I’ve found it needs much the same direction. If anything, the standard setting makes it too progressive, and pushes its way through the initial valving too quickly, which actually gives it a harsh feel. So I spent some time reworking that to give it a more balanced feel to match the revised front-end settings. Also, I actually dropped the bike’s rear- end about 3mm by machining the shock’s base-plate a little. It’s not a drastic change, but helps to level out the slightly ‘stink-bug’ stance the stock bike has. To be completely fair, the change to the fork does a lot of that, but this small rear-end mod complements it and helps to achieve that ideal chassis balance. And when a bike’s chassis is balanced, it’s a whole new animal to ride. A much better behaved animal!”

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To read more about Foster’s 350SX-F, pick up a copy of Transmoto‘s 2016 January-February issue (#54) on sale now. You can order a copy online, grab one at your local newsagents, or download a digital copy via the Zinio App – just search Transmoto once you’ve downloaded it on your favourite handheld device.