Clutch Maintenance and General Information
Inspecting Your Clutch Assembly
Riding style and proper maintenance are two main factors that affect clutch life. When inspecting your clutch plates and springs, be sure to also inspect all other related clutch components for excessive wear. Components such as the pressure plate, inner hub (clutch boss), cable, and basket may be worn as well. This is a commonly overlooked area when the time comes to replace a clutch. Many people think that when their clutch starts slipping or not shifting properly that it must be the clutch plates or the springs. This is not always the case. If the surface or the pressure plate and/or inner hub are excessively worn, it can change the pre-load on the springs and cause a clutch to slip- even a clutch with brand new plates. If your clutch basket or inner hub is severely grooved it can cause the plates to not release freely and result in poor shifting. Barnett offers billet aluminum clutch baskets for many popular ATV’s and off-road motorcycles. These clutch baskets are unique in that they utilize patented stainless steel inserts on the clutch fingers where the friction plate tabs make contact. These inserts prevent severe grooving of basket fingers and provides smooth, trouble free shifting and a longer clutch basket life. The Barnett baskets are also designed to increase oil flow to the clutch plates which keeps them cooler and extends clutch life. Barnett also offers billet aluminum pressure plates for select off-road models. These pressure plates include a tempered steel surface that Barnett guarantees to never wear out.
An improperly adjusted cable can reduce clutch life and performance as well. Make sure that your clutch cable is adjusted per factory specifications. Keep the cable and all pivot points clean and well lubricated.
When it comes to what oil to use in your clutch assembly, it never hurts to stick with the manufacturer recommended oils and viscosities. There are also many good quality full synthetic and synthetic blend oils available today. These oils are perfectly fine to use with Barnett friction materials. We do recommend, however, that you only use ‘motorcycle specific’ oil. Do not use oils designed for use in automobiles. Using oil designed for use in autos may reduce the life of your clutch and/or result in poor performance. The main purpose of the oil in the clutch assembly is to cool the plates. Therefore, the best thing for your motor and your clutch is to keep the oil clean. Changing the oil regularly is cheap insurance!
Inspecting your clutch plates and springs
When it comes to inspecting/replacing your clutch or any other components on your motorcycle or ATV, the best tool you can have is a factory service manual. The manual will provide you with all the specifications you need and show proper installation of all components. If you do not have access to a service manual, remember to take note of how all components come out and make sure that you re-install the components in the same order.
Overall Clutch Plate Stack Height
One of the most important factors in the clutch assembly is the clutch plate stack height. The stack height is the measurement of all friction plates and metal plates stacked together. The clutch stack height for new plates can vary slightly, but not to any great extent. In most factory service manuals, there is a minimum overall clutch stack height specified. Again, this varies from model to model. If your clutch is worn to the minimum stack height, it is definitely time to replace your clutch. It is also important to make sure that when you install a new clutch pack, it is the correct stack height required by the manufacturer. If the stack height is too thin, it can cause slippage and lead to premature wear. If the stack height is too thick, it can cause the clutch to drag resulting in poor shifting.
First of all, friction plates are consumable items that are meant to wear and consequently need to be replaced from time to time. The friction plates are designed to be a specific overall thickness. This thickness varies from model to model. Each manufacturer lists a minimum wear thickness for the friction plates. This number can be found in the factory service manual. This is one way to check the condition of your friction plates. However, this method is not foolproof. Often times, the friction plates may be above the minimum wear spec, but still not perform properly. The friction material, through the numerous heat cycles and abuse, can lose its friction capabilities and need to be replaced. The material can harden and glaze resulting in clutch slippage or clutch chatter. Again, if your clutch starts to slip or not shift properly, it could be the friction plates as well as other components (as stated above). Barnett offers high performance friction plates and complete plate/spring kits for all popular motorcycles and ATV’s.
Metal Drive Plates
The metal drive plates in the clutch assembly do not always wear at the same rate as the friction plates. As with the friction plates, each model requires a specific thickness for each metal plate. Some models require more than one thickness of metal plates in the clutch pack. When inspecting the metal plates, check to make sure that they are flat and not discolored from heat. If they are not flat or they are burnt from excessive heat, replace them. You can find the manufacturer maximum warpage spec listed in the service manual. Sometimes, the metal plates can be re-used as long as they are still the correct thickness and still flat. We recommend replacing the metal plates when you replace your friction plates. If you do decide to re-use your metal plates, you can bead blast them or lightly scuff them with a Scotch Brite pad or fine emery paper.
While, most models come with the metal plates made from steel, some models come with aluminum plates. The aluminum plates have a tendency to wear quickly, polish to a high sheen, and contaminate the oil. Replacing them with Barnett steel plates will help keep the oil cleaner, increase flywheel effect, and last much longer. Barnett also offers “Cryodized” aluminum drive plates for the serious racer. These plates are cryogenically treated and hard anodized for added strength and they do not contaminate the oil like plain aluminum plates. The “Cryo” plates are available for select models and recommend for racing applications only.
Another essential component for proper clutch operation is the clutch springs. Weak or fatigued springs are a prime cause of clutch slippage and premature wear. Again, similar to the clutch plates, each manufacturer has a minimum free length spec for the springs in each model. Refer to the factory service manual for the proper length required in your model. Barnett clutch springs are made of chrome silicon and are heat treated, shot-peened, and pre-set to remove initial sag. Barnett clutch springs are generally 15-25% stiffer than OEM springs. If you choose to use heavy duty clutch springs and you feel the lever pull is a little stiff for your liking, you can alternate them with standard springs if your motorcycle or ATV has an even number of springs (4 or 6). Remember that you must alternate them for even pressure on the clutch assembly. Often times you can install stiffer heavy duty springs to aid a slipping clutch. However, this should only be done as an emergency fix to get you through the day or through the next moto. This is only a temporary fix and the clutch assembly should be inspected right away and any worn components should be replaced.