WP XPlor 48 Fork Explained

The world of off-road motorcycle suspension is a complex one, and for riders of Husqvarna and KTM enduro machines, the evolution of WP's offerings has been a hot topic. For years, the WP 4CS fork, particularly prominent on Husqvarna models, faced a mixed reception. Despite numerous revisions, it struggled to win over a significant portion of the rider base. Many testers and riders reported a lack of sufficient damping, leading to the fork 'blowing through' its travel when ridden at higher speeds. As Enduro Editor Geoff Braico noted in ADB #440, "It doesn’t hold up even if the compression is clicked all the way hard." This dissatisfaction was compounded by the fact that many preferred the more traditional, and arguably more reliable, 48mm open-cartridge WP fork found on cheaper KTM models. This situation clearly wasn't ideal for the WP Group, prompting them to develop a successor.

Enter the WP XPlor 48 fork, introduced for the 2017 model year. This new unit was fitted to both KTM and Husqvarna enduro bikes, with Husqvarna retaining a point of differentiation through the inclusion of three-way preload adjusters on the fork caps. While the exact reasons for KTM moving away from their well-regarded open-cartridge fork remain somewhat unclear, the XPlor 48 has been widely praised, with most riders finding it to be an exceptional upgrade. WP's response to the unpopular 4CS was to create what many consider the "next big thing" in suspension technology, a decision that resonated positively with the market. Braico himself described the split system of the XPlor 48 as "plush" and "giving plenty of confidence to tip into corners at pace" in ADB #453. So, what exactly makes the XPlor 48 so effective, and how does it differ from its predecessors?

Understanding the XPlor 48's Technology

The WP XPlor 48 shares some core internal components with the previous open-cartridge fork. It utilises a 12mm damper rod, a 23mm cartridge tube, and a 28mm base valve. Crucially, both the XPlor 48 and the older open-cartridge forks employ unsealed and unpressurised inner cartridges, a departure from WP's closed-cartridge motocross suspension. The older open-cartridge forks featured rebound adjusters on the caps of both legs, controlling oil flow through the mid-valve to adjust rebound damping. Compression adjustment was handled via bottom plugs, influencing oil flow through the base valve.

The XPlor 48, however, presents a different configuration. The fork legs are asymmetrical, with all adjusters located on the caps – there are no bottom adjusters. The right fork leg is responsible for all rebound damping and approximately two-thirds of the compression damping, utilising stiffer valving for this purpose. A key difference lies in the compression adjustment. Unlike the older open-cartridge system, the compression adjuster on the XPlor is not directly linked to the base valve. Instead, it operates via a fixed-orifice valve. A plunger within this valve is moved up or down by the knob on the left fork cap, altering the size of the valve port. This mechanism is not progressive; the oil flow doesn't change based on applied force in the same way a shim-based valve would, meaning it has a more limited impact on low-speed damping. Additionally, the XPlor fork features cross-drilled holes at the top of the compression cartridge, designed to reduce pressure differentials. While this aids in pressure management, these holes can also limit the overall damping range the fork can produce.

Cosmetically, the most obvious difference is the location of the adjusters. Both legs contain springs and are filled with fork oil. The KTM version of the XPlor 48 lacks external spring preload adjustment, whereas the Husqvarna variant includes three-position preload adjusters on the top of each leg. These adjusters, while convenient, can sometimes interfere with the fitment of fork bleeder valves, with some owners resorting to modifying the triangular adjusters to accommodate them.

Why No Air Forks for Enduro?

A frequently asked question revolves around the absence of air forks in this application, and the reasoning is rooted in reliability and trailside practicality. Air forks rely on maintaining consistent air pressure within the cartridge for the front of the motorcycle to remain at the correct height. Any compromise to this seal – such as a damaged fork tube, a blown seal, or a leaking O-ring – can immediately end a ride. In contrast, if a spring fork encounters similar issues, it typically remains rideable, allowing the rider to return home. Another factor is rider preference; air forks can often feel stiffer and provide a harsher initial response compared to spring forks. This characteristic is less than ideal for enduro and trail riding, where riders spend extended periods navigating varied terrain and rely on the initial sensitivity of the suspension.

Tuning the XPlor 48

Out of the box, the WP XPlor 48 is generally set up for trail riding. For the more leisurely rider, the stock plushness is often perfectly adequate. However, for faster riders, heavier individuals, or those demanding a more performance-oriented setup, the stock settings might feel too soft. The limitation of the XPlor's compression adjuster is its minimal effect on low-speed damping. While winding it in can firm up the high-speed damping, the low-speed characteristics remain largely unchanged due to the adjuster's indirect connection to the base valve.

For those seeking more comprehensive adjustment and improved damping control across the entire stroke, aftermarket solutions are available. Companies like RaceTech Australia offer upgraded base valves that provide enhanced low- and high-speed damping characteristics. Furthermore, experienced riders may benefit from increasing the spring rates to better match their weight and riding style, coupled with a valving upgrade. While the Husqvarna's spring preload adjusters are a useful feature, for riders exceeding approximately 85kg, they are often insufficient to overcome the fork's initial soft feeling.

It's important to remember that manufacturers design stock suspension settings to cater to a broad spectrum of riders, not solely elite racers. This approach ensures a comfortable and functional experience for the majority.

Comparison: XPlor 48 vs. Open Cartridge

To summarise the key differences and similarities:

Frequently Asked Questions

Q1: How much oil does the WP XPlor 48 fork take?
For the 2018 Xplor fork, both legs take 635 millilitres of 4-weight oil. It's crucial to follow the correct procedure for draining and refilling to ensure accurate oil levels.

Q2: How do I drain the oil from the WP XPlor 48 fork?
To drain the oil, you need to remove the damping rods. This involves unscrewing the 17mm Allen key plug at the bottom of each fork leg. Once the rods are removed, you can drain the oil by working the damper rod in and out. After reinserting the rods, refill with the specified amount of oil to the top, working the rods up and down to allow the oil to circulate into the damping system. It may take a few attempts to get all the oil in.

Q3: Can I upgrade the damping on the XPlor 48?
Yes, absolutely. While the stock compression adjuster has limitations, aftermarket base valves and valving kits are available from specialist tuners to significantly improve both low- and high-speed damping performance.

Q4: Is the XPlor 48 a significant improvement over the 4CS fork?
Overwhelmingly, yes. The XPlor 48 is considered a substantial leap forward in performance and rider satisfaction compared to the much-maligned 4CS fork, offering a more compliant and confidence-inspiring ride.

Verdict

As a suspension tuner and motorcycle mechanic, my livelihood depends on manufacturers not completely perfecting suspension. However, I can confidently state that the WP XPlor 48 is a vastly improved fork. Whether it's the absolute best WP has ever produced is a matter of ongoing debate and depends heavily on individual needs and riding styles. Many racers still prefer the adjustability and feel of a custom-tuned open-cartridge fork.

However, for the intended purpose of trail riding, the XPlor 48's initial plushness is a significant advantage. It's forgiving on the arms during long rides and handles choppy or rocky terrain with a smooth, confidence-building action. For riders who push their bikes harder than the average trail rider, a professional suspension tune will unlock the full potential of the XPlor 48, addressing any perceived shortcomings in its stock configuration. It represents a monumental improvement over the 4CS, making it a worthwhile upgrade for any rider seeking a more refined and capable suspension experience.

This feature was first published in ADB issue #463 – April 2018

Words: Matt Boyd Pics: Olly Malone