WHAT’S SO GREAT ABOUT THE KTM CLUTCH & WHY ARE OTHER BRANDS COPYING IT?

This is a KTM clutch. It comes in two different versions—one for 450 four-strokes and 250 two-strokes and the other for 350 four-strokes, 250  four-strokes and 150/125 two-strokes.

People often ask why MXA raves about the KTM, Husqvarna and GasGas clutches so much. They want to know what makes theses clutches so different from other brands clutches. Let’s be clear, the standard clutches on most Japanese bikes are built with the best technology available in 2006. There is only one leader in modern clutch design, and it comes on the 2023 KTM, Husqvarna and GasGas machines. This clutch is head and shoulders above any other clutch—which the Japanese brands have started to realize.

HERE ARE SIX REASON WHY KTM’S CLITCH IS BEING COPIED SO MUCH

Hinson does make an aftermarket steel clutch basket for certain models of the YZ450F and CRF450, but you still have to swap the primary gear over to it.

(1) It comes with a steel clutch basket that never notches and will last as long as you own the bike, unlike the aluminum clutch baskets on the Honda, Suzuki and Kawasaki. Not only is the steel clutch basket stronger, but it can be lighter because it doesn’t need as much metal.

(2) Unlike a clutch with six separate coil springs, the Austrian clutch uses one large cupped Belleville washer that provides equal pressure across the face of the pressure plate.

(3) The Belleville washer can be preloaded for more or less tension by turning a stepped disc on the pressure plate.

(4) The KTM/Husky/GasGas clutch is activated by a hydraulic master cylinder and slave unit that self-adjusts as you use it. For 2023 KTM and Husqvarna motocross models use Brembo hydraulic systems and, if you got your 2023 GasGas from the first batch off the assembly line, it too will have a Brembo master cylinder and slave unit. However, if you got your bike from a later run GasGas bikes down the assembly, there is a good chance that your bike will have a BrakeTec master cylinder and slave unit. Why? Remember the pandemic, supply line issues and work shutdowns? Well, Brembo couldn’t supply all the clutch parts needed to fulfill the production demands for KTM, Husqvarna and Gas Gas. Rather than delay the delivery of bikes to the dealers any longer than necessary, the KTM Group had to change the spec—and Braktec, which handles the brake and clutch fitment on several Husqvarna off-road models got the call to supply the later arriving GasGas models with their systems.

Don’t know what clutch hydraulics your new GasGas has, look at the fine print on top of the clutch master cylinder—if it says Brakiec, then you don’t have Brembo…and you won’t have Brembo brakes either.

On the typical Japanese clutch you have to remove the primary gear by drilling out the rivets to move it to a new basket.

(5) The CNC-machined steel clutch basket has the primary gear machined into the billet of steel (instead of riveting a separate primary gear to the back of a cast aluminum clutch basket like the bies from Japan).

(6) Riders who burn up the standard issue KX450, CRF450, YZ450F or RM-Z450 clutches in four motos will go months with a KTM Belleville-washer clutch.

This is the DDS (Damped Diaphragm System) clutch that comes in the KTM 450SXF and 250SX two-stroke (it also comes on selected Husky and GasGas models). Six kidney-shaped rubber dampers (one of which is shown at the bottom of the photo) cushion the clutch from acceleration jolts.

Clutch models. There are two types of KTM/Husky/GasGas hydraulic clutches. First, the 450 four-strokes and 250/300 two-strokes come with the Belleville-washer-operated DDS (Damped Diaphragm System) clutch. It has a rubber-damped cush-hub inside to lessen the jolt when the more powerful engines hit. Second, the 250/350 four-stroke engine’s clutch is called a DS (Diaphragm System) clutch. It differs from the 450’s DDS clutch in that it doesn’t get the rubber-damped cush-hub. Why not? The 250/350 engines do not need to cushion the jolt of each gear because of their lower power profile. 

This is what a Belleville washer looks like. Instead of five or six separate coil springs, like on the typical clutch, a Bellevile washer spring applies equal pressure to the KTM pressure plate.

Belleville washer. A Belleville washer is essentially a large cupped washer that provides spring pressure as it is compressed. The first Belleville washer clutch came with a 250 N/m spring back in 2012. It was upped to 280 N/m in 2014. With today’s more powerful engines, the 2021 450’s Belleville washer is now rated at 295 N/m, while the 250/350 washers are 270 N/m. The Austrian engineers do not actually classify the spring pressure of the Belleville washers in N/m, preferring to call it “slip torque,” but for clarity’s sake, slip torque is the amount of spring pressure needed to control pressure plate and friction surface grip.

Lever pressure. One big plus of the Belleville washer’s cupped shape is that it is at maximum stiffness in the initial part of the clutch lever’s movement, but the farther the rider pulls the clutch lever, the flatter the cone shape of the cupped washer gets, which means that, unlike a coil-spring-operated clutch, a Belleville-washer clutch gets easier to pull the farther you pull it in. This relieves hand fatigue. In 2019, Kawasaki switched to a hydraulically activated clutch and for 2020 borrowed KTM’s Belleville washer spring design, but called it a “coned disc-spring clutch” to avoid looking like they copied the KTM design, which they did. However, they did not copy the CNC-machined steel clutch basket/primary gear combo. But for 2023 Yamaha is copying the whole kit-and-kaboodle (CNC-machined steel basket, milled-in primary gear, and Belleville washer spring on the YZ450F), but sticking with cable operation instead of hydraulics.

The notches in the tangs of this cast clutch basket are caused by the metal drive plates banging against the aluminum tangs during acceleration. The smooth action of a clutch in this basket would suffer greatly as the clutch plates get caught on the ridges.

Notching. The billet steel clutch basket will outlast any cast-aluminum clutch basket. Best of all, it will not notch where the metal drive plates hit against the tangs or suffer from tang breakage. The aftermarket clutch companies are loathe make a KTM clutch basket from aluminum. Why not? Most notably because the stock KTM basket is too good and practically because there are no bolt-on primary gears available. Hinson does make a steel clutch basket for the YZ450F and CRF450, but that is because they can use the stock primary gear.

Old school Magura master cylinders need mineral oil instead of brake fluid. It will be embossed on the master cylinder cap if required, but these mineral oil system are only on older models..

Clutch fluid. KTM/Husky/GasGas clutches can use Dot 4 or Dot 5.1 brake fluid. Some older Magura hydraulic clutches require mineral oil instead of brake fluid, but if that is the case, it will be embossed on the master-cylinder reservoir cap.