TEN THINGS: ABOUT CLUTCH WEAR & TEAR

(1) Clutch wear. When your motorcycle’s clutch is slipping, the amount of power transferred from the engine to the rear wheel is reduced, and your bike isn’t able to perform optimally. There are many factors that come into play with clutch wear, and most riders don’t realize what wears out a clutch until they get a lecture from their local mechanic. 

(2) Spring tension. Clutch springs come in a variety of sizes and strengths. They work together with the pressure plate to squeeze the clutch pack to engage the clutch. Once you squeeze the clutch lever, a push rod works against the springs to separate the plates and disengage the clutch. Softer springs allow for an easier clutch pull and less tension on the plates. Stiffer springs make for a harder clutch pull and added force on the plates. Stiffer springs are used to ensure a stronger clutch bite, which also increases clutch durability. As the clutch springs heat up and cool down over the course of a ride day, the materials begin to degrade. OEM springs are built specifically for each model and usually work well, but over time they will wear out and soften. 

(3) Plates. Motorcycle clutches utilize steel and fiber plates to engage the clutch. The steel plates rarely wear out, but the fiber plates wear down like brake pads every time the clutch engages. In most cases, fiber plates will grow thinner and discolor as they wear out. Sometimes, if used and abused too long, they’ll even break into pieces. 

(4) Rider skill. Ricky Carmichael and Kevin Windham both rode for factory Honda in 2004. They both rode CRF450s with Hinson clutches, and they competed at the same races. Ricky won every moto during the AMA 450 Nationals, while Kevin Windham was second overall four times and third overall four times that year. Honda threw everything they had at Carmichael’s bike, but they still had to replace destroyed clutch parts often. Kevin Windham was riding with the same equipment, but because of his smooth riding style, he was able to use softer springs and his clutches lasted much longer than Ricky’s. Similarly, in 2020, Supercross racer Ken Roczen abuses his clutch much less than his teammate Justin Brayton. The difference is that Carmichael and Brayton twist the throttle while slipping the clutch lever at the same time more often than Windham and Roczen. 

(5) Lever ratio. Because the pressure plate only moves a small distance to disengage the clutch, any change you make to the lever and perch ratio can affect the engagement point. It’s important to use model-specific geometry when installing aftermarket levers and perches on your bike. Works Connection and ARC Levers are two aftermarket companies with a reputation for keeping the intended ratio.

(6) Oil. As the plates wear down, not only do they have less friction to grab onto, the oil is also contaminated with the fiber-plate particles. These particles float around the engine oil and diminish the traction between the plates. Often, a slipping clutch can be temporarily revived by changing to fresh oil. 

2020 Yamaha YZ250F clutch

(7) Inner hub. Like radiator fluid in a radiator, engine oil works to keep the clutch cool and operating properly. Aftermarket inner hubs are more efficient because they work together with the pressure plate to retain oil and direct it to the plates rather than the cases. This keeps the temperature down and increases durability.

(8) Basket. The clutch basket not only holds the plates, fibers, inner hub and pressure plate inside the clutch, but it also is connected to the engine’s crankshaft. The teeth on the external portion of the fiber plates mate with openings in the basket. Over time, the constant friction between  plates and the basket’s tangs can create notches. The notches make for harder shifting and clutch slipping. You can file the notches smooth again to temporarily fix it, but eventually the basket needs to be replaced. 

(9) Actuation. Hydraulically actuated clutches have a smoother pull that is more desirable for riders; however, their one flaw is that you can’t tell when the clutch is overheating. Cable-actuated clutches develop slack and have more free-play at the lever when they heat up. This serves as a warning for riders and helps them monitor their clutches. 

(10) Aftermarket. When a clutch is precise, it doesn’t work as hard to engage or disengage. This translates into less heat. Aftermarket companies like Hinson and Rekluse make their own clutch baskets, inner hubs, pressure plates, springs, fibers and steels to ensure optimal efficiency. With less wiggle room, the clutch strength and durability are increased.

 

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