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February 17, 2010
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WHAT IS IT? A set of clutch internals that eliminates the need for you to pull the clutch in.

WHAT’S IT COST? $799.00.

CONTACT? www.rekluse.com or (866) 735-5873.
WHAT’S IT DO? The Rekluse Core EXP (often called the z-Start Pro) clutch is a retrofit automatic clutch. Unlike a conventional clutch or a slipper clutch, the Rekluse Core EXP clutch disengages the clutch whenever the rpm falls below a preset level. Then, when you accelerate, the Core EXP clutch re-engages. There is no need for the rider to ever touch the clutch lever when moving or stopping (although the Rekluse Core EXP does allow the rider to use the clutch on the start or any time he wants). How does it work? It uses centrifugal force to engage and disengage the clutch (the centrifugal force comes from turning the throttle on and off).

Although designed as an offroad product for woods, enduro and Endurocross riders, the z-Start Pro clutch was used to great effect by Sean Collier last year in the 450 Nationals. The new Rekluse Core EXP is an improvement on Collier’s race clutch.

WHAT STANDS OUT? Here’s a list of things that stand out with the Rekluse Core EXP clutch.

(1) The parts. The Rekluse Core EXP clutch comes with a billet-aluminum inner clutch hub, pressure plate, EXP assembly, drive plates, clutch springs and a gasket. The Rekluse clutch uses the OEM friction plates and clutch basket. Everything to complete the installation is provided in the kit.

(2) Function. Forget everything you know about Rekluse automatic clutches. The previous version worked by using centrifugal force to spin 27 steel balls away from the center of the Rekluse’s ball-ramp pressure plate. The more rpm, the farther the balls traveled up the groove-like ramps, and the farther the balls moved up the ramps, the more they engaged the clutch. No more!

It is not often that an inventor is able to completely break away from his watermark idea, but Rekluse’s Al Youngwerth did just that. The 2009 actuating mechanism is totally different. The new Rekluse Core EXP clutch is simpler to install, easier to adjust, less complicated and more compact. Gone are the steel balls, the groove-like ramps and competing pressure plates. Instead, the Rekluse Core EXP has compressed all the inner workings into a small, half-inch-thick clutch pack called the “EXP assembly.” The EXP assembly (EXP stands for expansion) is basically a small slinger clutch system sandwiched between two clutch plates. Although it is a single unit, there are sliding weights that are spun outward (inside the sandwich) to expand the EXP assembly. Thus, when the rpm increases, the weights slide outward to spread the EXP assembly wider. This widening action hooks up the clutch. When the rpm drops, the weights slide inward and the clutch is disengaged. Very neat. Very tidy. Very foolproof.

(3) Adjustment. All adjustments are done by changing the springs that hold the weights in place. We opted for the stiffest springs to make the automatic effect kick in with the most bite. Offroad riders often go for a softer and more modulated bite.

(4) Installation. There is no need to take the stock clutch out of your engine. The OEM basket stays. The Rekluse Core EXP parts replace the stock inner hub, steel plates and pressure plate. As an added bonus, you can change your Core EXP automatic back and forth from fully automatic to fully manual just by installing Rekluse’s optional Manual Pressure Plate.

(5) Clutch lever. The Rekluse Core EXP maintains a stock clutch lever feel, and you can pull the clutch in manually at any time and any rpm.

(6) Clutch wear. The Rekluse Core EXP clutch is not a true automatic in that you still have to shift. It is more like a Porsche Tiptronic. As for wear, since the clutch actuation is robotic, as opposed to ham-fisted, clutch wear seems to be less than on a stock clutch.

(7) Weight. The Rekluse Core EXP weighs a little more than the stock clutch, but only because of the sliding weights in the sandwich-like EXP pack. This can be a benefit on some bikes and a detriment on others, but since a clutch spins at one-third engine speed, the flywheel effect is minimal.

(8) Clutch override. The ability to disengage the clutch (and re-engage it) with the clutch lever is a major plus over the older version of the z-Start. It allows the rider to energize the powerband for whoops, jump faces, corner exits and starts.

(9) Stalling. You can’t stall. Okay, you could probably figure out a way to make it happen, but it won’t be because the Rekluse Core EXP clutch didn’t try to save you. You can jam into a corner at full tilt, and when you chop the throttle, the clutch will be disengaged. Most four-stroke riders already depend on an educated clutch hand to keep from stalling. The Core EXP clutch eliminates the need to have your left hand on alert.

(10) The start. Nothing weird. Start just as you would on a normal bike by using the clutch lever. No difference. If you want, you can put your bike in gear and sit on the starting line with the engine idling. Then when the gate drops, you can just go?no clutch lever needed. With the Core EXP clutch, the bike won’t move until you turn the throttle.

(11) Gear selection. We started running a gear higher in all the corners. Once the fear of stalling is eliminated, there is no reason not to bomb in, chop, and bomb out.

WHAT’S THE SQUAWK? Most motocross racers spend years learning how to maximize the rpm, clutch and transmission interface. It is a learned skill, and the Core EXP clutch is counterintuitive. MXA test riders had to learn not to pull the clutch in when they came to a stop.      

This simple little device eliminates the need to ever pull the clutch in again. That is an earth-shattering concept. Just gas and go?no levers. The MXA wrecking crew gives the Rekluse Core EXP clutch five stars (especially for Novices, Vets and riders with stalling problems). Sean Collier proved that National Pros can use the technology, too.



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