ThumperFaq: MXA Bulletproof Clutch

Motocross bikes depend on oil-lubricated clutch plates to provide full hook-up of the engine's ponies. If your bike doesn't have a strong clutch, you won't be going any faster than your gardener's weed whacker. Here are ten fixes that will help you avoid a slipping clutch.

NUMBER ONE: GO FOR STIFFER SPRINGS

Your bike was delivered from the factory with the lightest-feeling clutch pull imaginable. Manufacturers are willing to give up longevity to achieve the perfect showroom feel. The easiest way to make your clutch last longer and work better (short of not using it) is to stick in stiffer clutch springs. For example, 125 riders can put 250 clutch springs in their bikes. You don't have to put stiffer springs in every hole. You can put in two or three stiffer springs to suit your personal clutch-lever pulling power.

NUMBER TWO: CHANGE THE OIL FREQUENTLY

Change your bike's tranny oil every two races. That is a lot of oil, but it is worth it. Fresh oil washes away contaminants and extends the life of your bike's clutch plates.

NUMBER THREE: SHIM THE CLUTCH SPRINGS

If you can't find stiffer springs and you develop clutch problems on race day, the quickest fix is to shim the clutch springs with washers. Put the washer under the bolt. The space that the washer takes up will preload the spring and provide more tension.>

NUMBER FOUR: AUTOMATIC TRANNY FLUID

You don't have to run standard transmission oil in your gearboxyou can run automatic transmission fluid in a pinch. ATF will not only lubricate your gears, but, if you use GM-type ATF, it will improve the grip of your clutch. GM automatic tranny fluid is a grippy type of fluid that improves the interaction between the drive and driven plates. Don't use Ford-type ATF, because it is a slippery formula.

NUMBER FIVE: TOSS THE ALUMINUM PLATES

Most modern clutches have aluminum plates. They save weight but they wear out faster, contaminate the oil quicker and are more prone to warp under intense heat than good old, heavy, steel clutch plates. If you want a durable, long-lasting clutch, switch your bike back to steel clutch plates.

NUMBER SIX: SAND THE GLAZE OFF

If your clutch is beginning to show signs of slippage, you can forestall the inevitable by removing the fiber clutch plates and resurfacing them. The best way to sand the clutch plates is to tape a piece of sandpaper to a flat surface and rub the fiber plates against the sand paper. Don't over sand the fiber plates, just break the glaze.

NUMBER SEVEN: SPEND A QUARTER

A lot of clutch problems are caused by riders running their clutch levers too tight. If you walk over to your bike and lightly touch the clutch lever, it should have freeplay in it. The rule of thumb is that there should be enough freeplay in the clutch lever to stick a quarter between the lever and the lever perch without the cable getting taut.

NUMBER EIGHT: BASKET CASE

Clutch plates fit inside an aluminum basket with ten or eleven tangs sticking up. When you pull the clutch lever, the plates slide up and down inside the tangs. Unfortunately, they also bang back and forth as the power is turned on and off. This banging wears notches in the basket tangs and the notches interfere with the up-and-down motion of the clutch plates. If the grooves get too deep, you will have to replace the complete basket. But if the grooves are not too bad, you can file them out. This is, at best, a temporary fix, though, because with each filing you are making the space between the tangs and the clutch plates wider. This increases the amount of banging when the power is supplied.

NUMBER NINE: BRAND-NEW PLATES

All the tricks in the world won't help if your clutch plates are worn past the manufacturer's wear tolerances (found in your owner's manual or by asking your dealer). Measure the plates. If they are worn out, replace them!

NUMBER TEN: THE ULTIMATE FIX

Buy a Hinson clutch basket (you can reach them at [9091946-2942). Hinson is the leader in replacement clutch baskets, clutch hubs and pressure plates for motocross bikes. Following all the fixes above and installing a Hinson clutch basket is the ultimate clutch upgrade. Hinson's clutch baskets are designed with windows that force more oil into the clutch assembly, helping dissipate heat and increasing clutch-plate life.