You hear the term "A-Kit" thrown around a lot in the moto­cross world. Kit suspension is the closest thing us mere mortals can come to factory-level suspension. In fact, some factory suspension pieces are used inside "kit" suspension that is available for you to purchase. But just what does kit suspension feel like and how much better can it be than your stock production suspension that comes on your motorcycle? What makes kit suspension the best dirt bike suspension you can buy?

Not everyone has a set of these expensive pieces to go out and try before making that purchase to see if it really makes their dirt bike handle better and if lap times drop when the track gets rough. This is where Dirt Rider comes in. We went and got a set of KYB (2017 Yamaha YZ450F), Showa (2017 Honda CRF450R), and WP (2017.5 KTM 450 SX-F Factory Edition) kit suspensions and put in several hours at many different tracks to really see what the differences are between the production suspension and kit stuff you can buy through your local authorized suspension dealer.

We break down A-Kit dirt bike suspensions and compare them to their stock counterparts, trying to find out if they are worth the premium price.
KYB (2017 Yamaha YZ450F), Showa (2017 Honda CRF450R), and WP (2017.5 KTM 450 SX-F Factory Edition)Sean Klinger

Testing A-Kit Dirt Bike Suspension

These three companies—WP, Showa, KYB—offer their A-Kit suspension for all brands of motorcycles, but we wanted to keep it uniform and put them on the dirt bikes that each brand comes stock on. We tested at multiple types of tracks in Southern California and went through several valving setting changes to find a good baseline to give the proper feedback.

Just like when you send in your stock suspension to get revalved, it might take more than just one adjustment for your local suspension shop to get it set up for you. The A-Kit suspension is no different, and it will demand some patience and testing on your part to get it to where you will enjoy its full benefit.

Testing The KYB Kit Suspension On The Yamaha YZ450F

Price: Fork $4,500 | Shock $2,650

The 2017 Yamaha YZ450F suspension is the best dirt bike suspension out of the 2017 models we had ridden. It moves in the stroke and has tons of comfort, and the KYB kit suspension is no different. Based on the KYB AOS (Spring Fork) System, the KYB kit fork comes with dark Kashima coating on the outer tubes with outer tube protectors, DLC coating on the inner fork tubes, black anodized billet axle brackets, and the inner cylinders are dark Kashima coated. The KYB kit shock incorporates the KYB triple adjuster with high- and low-speed compression along with the rebound on the clevis, dark Kashima body, and DLC-coated shock shaft.

The ride on the track is not a lot different than the one you feel from the production-based suspension. The biggest difference is in the fork’s action. The action (or movement) is still familiar, but instead of the damping feeling a little empty near the end of the stroke, the KYB A-Kit fork is super firm at the end. The top of the stroke is very plush and moves while giving you great front tire contact.

The front tire contact patch on the KYB kit fork feels bigger than stock when leaning the bike over in corners. This is from less movement in the mid-stroke (increased damping feel) as the fork (front end) of the Yamaha doesn’t want to react as quickly to the rider’s throttle hand. What is unique about the KYB kit fork is that with the other two brands of kit forks you are losing a little comfort to gain performance, but with the KYB kit fork it feels like the advantages in performance and comfort are equally matched.

The KYB kit suspension on the Yamaha YZ450F firms up the fork action, without making the ride uncomfortable.
The KYB kit suspension fitted on our Yamaha YZ450F test bike.Sean Klinger

The KYB kit shock is easy to adjust, as everything that you want to adjust is right on the clevis. The rear end felt a little firmer initially but still gave the Yamaha plenty of traction with a sag setting of 102mm. The kit shock planted the rear end of the YZ450F on braking bumps and kept the big Yamaha from wallowing on rollers. It only took two valving settings to get the kit suspension feeling better than that of the stock suspension, and we could dial in the clickers easily no matter what type of track we rode at.

Unlike the stock Showa suspension, the kit pieces do not feel soft after breaking in.
Testing the Showa kit fitted on our Honda CRF450R.Sean Klinger

Testing The Showa Kit Suspension On The Honda CRF450R

Price: Fork $5,650 | Shock $4,150

The 2017 Honda CRF450R comes with a 49mm Showa coil spring fork, and overall the feeling of the bike—at both ends—is soft for most racers once broken in. Showa's new A-Kit fork retains its 49mm standard size but uses a larger sized piston, a 39mm subtank, dimple processed outer tubes, and billet bottom lugs. The shock uses an 18mm shock shaft, 30mm compression adjuster, 50mm billet shock body, and a candy-red lightweight steel spring.

The Showa A-Kit suspension has a much different feel than that of its stock brother. The Showa fork and shock took me some time to get set up for my liking, and after three setting changes to the A-Kit suspension—to make it less firm and get more front-end feeling—I had a good base to test from. The fork action feels like it’s made for the aggressive rider. The farther up I rode on the Honda and the more aggressively I rode, the better the Showa A-Kit fork performed. It retains a firm feel throughout the stroke and gives the CRF450R less pitching.

The fork likes to be set at 2 to 3mm up in the top clamp; any higher than that, the Honda will have too much under-steer. Another tip when going to a firmer fork setting is to purchase a set of 2017 CRF450RX engine hangers. The softer engine mounts will give you a more compliant feeling when hitting square edges and an increase in front-end traction while maintaining the firm fork feel that you want out of the A-Kit fork.

The Showa rear shock also has a firm feel throughout its stroke and feels the best at around 106 to 108mm of sag. The rear of the Honda is more active but has better bottoming resistance than the stock shock. On braking bumps, the feeling can be described as firm and can scare off nonaggressive riders. The Showa shock loves large amounts of throttle and will reward you by squatting and hooking up coming out of corners when doing so. The Showa A-Kit suspension is best suited for an aggressive rider or pro-level rider who needs more hold-up/performance in their suspension.

Testing The WP Suspension On The KTM 450 SX-F Factory Edition

Price: Fork $3,599 | Shock $2,449

WP offers two types of A-Kit level forks: a 48mm Cone Valve spring fork and a 48mm Cone Valve AER fork. Since we tested the Cone Valve spring fork last year and the KTM 450 SX-F Factory Edition comes with the 48mm WP AER system, we wanted to try the latest A-Kit fork offering, which is the 48mm AER Cone Valve system along with Trax shock.

The AER Cone Valve fork is more than 2 pounds lighter than the standard Cone Valve and uses two air chambers—unlike the stock AER fork which uses only one—along with the Cone Valve technology. The Trax shock system registers when the rear wheel has no ground contact and immediately opens an oil bypass, so the rebound can expand faster in order to contact the ground quicker.

The WP AER Cone Valve fork feels the most performance-based out of the kit suspensions tested.
Riding the WP kit suspension on the KTM 450 SX-F Factory Edition.Sean Klinger

On the track, it was apparent imme­diately that you were riding with performance-based suspension. Unlike the Showa and KYB suspension, the WP set is very dead feeling, meaning it doesn’t move or react quickly. The feeling between the stock suspension and the kit stuff feels firmer, but when riding at 75 percent it won’t beat you up. The fork takes some time to set up and check before making your way on the track, but it has a similar feeling to that of a spring fork. It moves initially in the first part of the stroke yet firms up through the middle to end without much harshness to the rider.

The huge benefit to the AER Cone Valve fork is that you can jump out into the flat or charge into deep braking bumps and the front end will not dive or deflect. The fork soaks up more with less pitching than the stock fork. The AER Cone Valve fork also takes away the harshness of small hard-packed acceleration chatter bumps and gives the rider as good of front-end traction as the stock fork, which is rare in a firmer-feeling fork setting.

The Trax shock’s rebound system (the bypass that allows fast rebound when the rear wheel isn’t on the ground) can be turned on or off by your local dealer when setting up, but I found I liked the system turned off to get that “dead feeling” that I wanted out of the bike’s rear.

Not all A-Kit suspensions are equal. When purchasing a suspension kit, one needs to account for the weight of the rider, riding style, and what kind of suspension feel the rider prefers.
A-Kit suspension from KYB, Showa, and WP.Sean Klinger

Should I Upgrade My Dirt Bike Suspension?

At the end of the day, your wallet is going to make the decision for you, as this is not a cheap investment. Yes, these sets of suspension are expensive and not everyone is going to benefit from getting A-Kit-level suspension. Most casual riders will never outride their stock settings. However, if you’re serious on performance and have the extra dough, each one of these sets of suspension is unique and can bring a level of confidence to your riding, knowing you can charge harder in every section of the track.