Before you begin any clutching mods or repairs on your sport quad, you should run right out and buy a factory service manual for your particular machine. These usually sell for anywhere from $30-$50 and are an invaluable investment if you want to work on your own machine. Inside it will be the official factory specifications and tolerances for your ATV. It is vital to know the official torque specs, clutch plate and spring specs, and factory tolerances of these components before you start your own clutch work.
Hinson Racing makes a replacement clutch kit for sport quads that includes a new basket, new springs, and new fiber and metal clutch plates. This can help give your sport quad an edge out on the trail or the track.
Next, drain the oil from your machine. On machines with separate oil tanks, make sure you also drain the oil out of this oil tank as well. Then, take off the clutch cover. Be careful to lay out the parts you remove in an orderly fashion, not in a pile. This makes the job go back together quickly and easily and in the proper order.
Remember to visually inspect all components and clean them thoroughly. Check the bottom of the clutch case for chips, chunks, shavings, parts, etc. You might have other problems. Take the friction and metal plates and stack them like “pancakes.” This is a good way to see if they are flat or not.
Hold the stack up to the light. If you find any air gaps or light gaps, they need replacing. Also, if they are burned, scored, warped, bent, chipped, glazed, or if the thickness is not to factory specs, (consult your shop manual) you need to replace it.
All the plates stacked together should make a nice flat package. If the components are inspected and/or replaced in this manner, you shouldn’t have problems like dragging, hard to find neutral, or hard to shift issues.
CLUTCH FRICTION PLATES
The “heart” of ATV clutches are the friction plates. They are what take the most abuse, wear and tear. Friction plates are designed as consumable items. They are meant to wear and, consequently, need to be replaced from time to time. Certain things can be done to increase their life in your ATV.
First of all, choose only the best available replacement components. Barnett and Hinson Racing make quality replacement clutch components. Be sure all related parts, such as the steel drive plates, springs, clutch hub, pressure plate, outer basket, clutch cable or hydraulic system, etc., are in top shape.
Always use good quality, clean, fresh oil, at the proper level and viscosity. Also, keep your clutch adjusted properly. Riding style can greatly affect clutch efficiency and life. Excessive slipping or “fanning” of the clutch can create excessive heat, resulting in premature wear.
METAL DRIVE PLATES
Since proper clutch operation depends on all components working together efficiently, the metal plates must be the correct thickness of and absolutely flat. Most O.E.M.’s produce metal plates that are identical, except for thickness, for use in many different models.
Always measure the thickness of replacement metal plates to assure proper fit. Some models may require more than one thickness metal in the same clutch pack. The metal plates may be re-used if they are the correct thickness and meet flatness specifications. If they are discolored from heat, show “hot spots,” or are in any way suspect, replace them!
Some models utilize a spring or damper plate. This consists of two metal plates riveted together with a wave-washer between them. Always check the rivets and replace the plate if they are loose.
Remember, small pieces of metal floating around in your clutch assembly can lead to costly repairs. Many off-road models come stock with aluminum metal plates. These have a tendency to wear quickly, polish to a high sheen, and “muddy” or contaminate the oil. Replacing them with steel plates will keep the oil cleaner, increase flywheel effect, and they will last much longer.
When installing steel drive plates, notice that there is a rounded edge on one side of the plates and a sharp edge on the other. It is important that you install the steel drive plates with the like edges going the same direction. It doesn’t matter if the rounded edges or the sharp edges are facing outward, as long as the edges are facing the same direction.
Another area that is essential to proper clutch operation is adequate clutch spring tension. Weak or fatigued springs are a prime cause of clutch slippage and premature wear.
However, poor clutch action cannot always be solved by increasing spring tension. Many factors can figure into clutch slippage—such as worn or warped friction or metal plates, pressure plate and/or hub wear, cable stretch or flex, or improper adjustment of the clutch lever.
Excessively heavy springs can also cause problems such as stress or fatigue to clutch activators, case covers, center hub, damage to the pressure plate, broken post, or cable stretch—as well as being very hard on your left hand.
One helpful hint for dialing in your clutch is to alternate the stock springs with heavy duty springs. This can be done on applications that have an even number of clutch springs (4, 6, etc.). When doing this, it is important that the springs are alternated so the pressure is distributed evenly. This will also keep the clutch lever pull from being overly stiff.
As far as what oils to use, we generally suggest following the manufacturer’s recommendations. Use good quality engine-specific oils and lubricants. The main purpose of oils in a “wet” clutch application is to act as a coolant. Oils flowing through the clutch plates help to keep the plates cooler, resulting in smoother clutch action and longer life. Using too heavy viscosity an oil can cause plates to stick when cold.
Synthetic oil, by its nature, has extra lubricity. This can be a real advantage for the engine, but a disadvantage for a wet clutch.
To access your machines manual clutch components, tilt the machine on its side then remove the clutch cover from the engine. Keep in mind that the clucth cover bolts may be different sizes, so if you can, leave them in the cover when you remove it. Next, remove the retaining bolts and clutch springs.
With the springs and pressure plate removed, you can remove and inspect the fiber clutch plates. A healthy clutch should have meat left on the individual pads or friction squares of the plates. They should have a brown, not a black or burned look to them.
In between each fiber plate is a steel plate. On this engine, the steel plates have tiny dimple gauges so you can monitor how they are wearing. If the dimples are starting to disappear or the steel plates are warping, it’s time to replace them.
One of the key areas to inspect on your clutching components is the ears or fingers of the clutch basket. When they start to wear, small groves will appear where the fiber plates ride. You can also feel that this is happening if your clutch lever gets harder to pull.
HOW TO INSTALL A NEW CLUTCH
Check all plates for flatness. Look to see that the stack height is correct. Also check the springs are the correct height and tension. Check service manual for these specifications.
Pre-oil or soak the clutch plates (if wet type) in clean oil for about five to ten minutes. Soak in the same oil going into the ATV.
Check the plates slide into the basket and over the hub freely with no binding. If the basket is notched or fatigued where the clutch tabs go, it is best to repair or replace the basket or hub so further problems don’t occur. Make sure the clutch basket is working properly so it doesn’t create a chattering problem. Have your local dealer check it for you if you’re not sure.
Install the plates as per your owner’s manual and check specifications. Replacement plates should go in the same way the old plates came out. Determine the O.A.T. (Overall Thickness). This is the combined thickness of all steel and friction plates.
Basically, this must not vary, to any great extent, from stock. You can use more or fewer components, but stack height must remain the same. Too thin a stack may result in slippage, while too thick a stack may cause drag.
Install the pressure plates, checking to see if your ATV has a dot, arrow, or notch marked by the factory, they line up for proper function of the pressure plate. These marks are on some models but not all of them. The marks are on the clutch hub and pressure plate. Also, be sure to check the pressure plate along with the backing plate (the two surfaces the friction plates touch) for wear and flatness. An uneven or worn surface can ruin your clutch.
When installing the clutch springs, visually inspect your springs for uniformity and tension. Check your service manual for spring length. Weak springs can cause slipping—especially at high rpm.
Check the release mechanisms are properly working and do not show excessive wear. This can cause improper clutch adjustment, dragging, hard to find neutral, or hard shifting problems.
Lube cable, lever pivot and actuator, as needed. Check the cable is routed correctly and has no sharp bends or binding when turning the front wheels from side to side. Remember, smooth operation will allow you to properly adjust the clutch.
Be sure to torque all bolts to factory service manual specs. Use a new gasket when putting the clutch cover on, making sure to clean the gasket surface first.
Follow the manufacturer’s specifications on oil viscosities and quantity. Remember, the heavier the oil viscosity, the more the clutch plates tend to stick or drag when cold.
Another common concern is what type of cable lube should you use?
That depends on the type of cables used, and whether they are Teflon, nylon, or HDPE lined. Cable end fittings should be kept clean and lubed with a light grease or oil. If you wish to lube the internal cable, use a silicone spray, Teflon spray, or dri-slide, etc. Do not use heavy oils or grease that can attract dirt.
How about when it comes to cleaning the clutch plates? It’s a good idea to lightly scuff the friction plates with a Scotch Brite pad to remove any shine and glaze from the surface. Be sure to soak the plates in oil before re-installing them. Steel drive plates can also be scuffed with Scotch Brite or bead blasted to help seat them in.