HOW-TO: CLUTCH MAINTENANCE

On Jul 17, 2022

Inspect, clean, repeat By the staff of Dirt Wheels

Off-roading means dust, and dust is enemy number one for CVT clutches. Regular cleaning and inspections can extend clutch life. We’ve seen UTVs with over 4000 miles that never had the clutch cover off. Periodically remove the clutch cover and blow the clutches out with compressed air. You may need to blow them out after each ride if the dust is bad enough, but much more often than you’re doing it right now.

Most dirt powersports enthusiasts think dust is annoying when they’re out riding, but sometimes—many times—it’s more than annoying. It can be downright destructive, especially to your clutches.

Now, if your vehicle’s clutches could talk, they would same the same thing: “Dust is annoying and is not only hard on your primary and secondary, but it can also shorten the life of all those drivetrain components. It’s safe to say that dust is enemy number one for your clutches.

Many owners are hesitant to check on their vehicle’s clutches because they can be a little intimidating. A CVT looks simple, but there are sheaves, springs, helixes, weights, bushings and more. There are the special tools required to service CVT clutches, but you can lengthen the life of your clutches without being a master mechanic or having special tools.

It shouldn’t come as a surprise to any side-by-side owner that there are CVT maintenance steps you should perform on a regular basis. Some of those steps should be taken after every ride, some a little less often and others at least once a riding season.

We asked two separate clutch/drivetrain experts for their recommendations. Each has years of experience in the powersports industry. Matt Hasara was part owner of a powersports dealership before accepting a teaching position at Utah Valley University in Orem, Utah. He is now an assistant professor in the Department of Transportation Technologies at UVU (www.uvu.edu/auto/). The other is Jerry Mathews, part owner of Starting Line Products (www.startinglineproducts.com) in Idaho Falls, Idaho. Mathews has more than 30 years’ experience in the powersports aftermarket accessories, which includes clutching.

This clutch is from a new machine with a filtered intake grate and less than 400 miles on it. It clearly has not been cleaned often enough. When dust and dirt get sucked into your clutch intake, it circulates in the clutch area, penetrating the bushings, bearings and sliding surfaces and causing them to stick and bind, which results in excessive heat, premature clutch wear and eventual clutch component and/or belt failure. Whether you use compressed air, brake cleaner, water, or steam (Matt Hasara’s preferred method) to clean these things, just clean them. Belt dust kills clutch components. It might as well be grinding compound. Get it out of there.

Wear and tear are normal parts of dirt powersports, and that includes clutch components. These well-worn clutch weights (middle and right) sit next to a new weight, allowing you to easily see the difference. The top working surface of the weight should be smooth. Weights can wear much worse than this.

Inspect your clutch components, otherwise you might not notice the damage that happens with prolonged use and improper maintenance. The wear marks on these weights show catastrophic damage and loss of material. That wear can affect other parts of the clutch as well as your ride experience. Some weights are worn evenly but others are worn deeper on one edge showing evidence of wear on the pins and bushings.

The outside rollers on the secondary clutch roll up and down as the secondary opens and closes. Each time the clutch cover is removed, Jerry Mathews advised, inspect the driven clutch rollers or square slide blocks. The dustier the conditions, the more you should be inspecting the rollers. If rollers flat-spot, replace them as a pair. When they flat-spot, the roller is skidding on the tower of the clutch. The aluminum tower will wear, and the entire clutch might need to be replaced. Some clutches use slide blocks instead of rollers and there are varying opinions on which is best. Our experience is that rollers cause less friction and thus are more efficient.

This is another clutch that hasn’t been kept clean. For driven clutches with square slide blocks, Mathews says to inspect the slide block and aluminum tower that the slide block rides on for wear. It’s easy to see even the slightest wear on the towers. If wear is detected, the slide block can be removed and rotated 90 degrees one time to extend the life of the slide block. Some experts feel rollers have less friction and are more effective than square slide blocks.

Consider replacing square blocks with heavy-duty rollers. Heavy-duty rollers don’t flat-spot easily. They get up to four times longer service life. Some new machines are coming stock with metal rollers that have sealed bearings inside. They should have outstanding life.

Whether you’re working on a Ferrari or a lawnmower, a good visual inspection of the machine you are working on is a must. Even though it is acknowledged that rollers are superior for CVT operation, they are not infallible. From the wear on this “roller” it is apparent that it no long rolls. This will have damaged the surface it was supposed to roll on as well.

Mathews suggests periodic inspection of CVT weights, weight bushings and spider rollers when you have the cover off. He said, “If you are running hard in dirty or hot conditions with a heavy load like sand or mud, this inspection should be done at least every 500 miles.” There are stock and aftermarket weights that come with replaceable bushings. When the bushings get excess play, the tips of the weights will move over on the spider roller. This side-loading of the roller will cause the roller bushing to fail. If the roller bushings are worn, the entire roller and pin that it rides on must be replaced. Replace all three even if only one roller/pin assembly is worn. If the clutch components, like the bushings, get too worn, the weight as well as the spider assembly becomes damaged, requiring full clutch replacement.

Jerry Mathews recommends carrying a spare belt on your UTV and Matt Hasara suggests staying with an OEM belt when a change is needed. There are excellent aftermarket belts available, but brand name and price will not always guarantee a good choice. If you don’t have experience with the various aftermarket brands, it will save time and money to go with a stock belt. Some drivers carry a belt that is already broken in. Do not clamp a belt down too tightly if you fasten it to the car. Don’t force the belt to make tight bends.

This is what a severely abused belt looks like. The belt didn’t break, but it has been overheated and has transferred burned rubber onto the faces of the sheaves. The sheaves must be cleaned, deglazed and a new belt installed.

Matt Hasara says it’s important to drive in the right gear (high or low), depending on the conditions. Some UTV drivers tend to drive in high all the time. There are times low is better for the clutches and vehicle. In fact, Hasara says driving in low actually “helps” your vehicle. A good rule of thumb: switch to low range any time you are under 20 mph with a load on the engine and transmission. If you read that book that nobody reads—the operator’s manual—you’ll see that most manufacturers recommend using low range at elevation or during prolonged low-speed driving. This is especially true if you have a machine with a smaller engine (below 700cc). Trying to run at top speed all the time is very hard on clutches and belts. At speed the belt rides at the same spot on the sheaves, and that heats the sheaves. Varying rpm moves the belt around on the sheaves to keep belt temps down.

These clutches are waiting to be serviced by Jerry Mathews, who completely disassembles each clutch to inspect every component. Most UTV owners don’t have the tools or experience to do this work. If you don’t have the proper tools a trusted powersports dealer or shop might be your best option. Most clutch kit companies sell the needed tools if you want to try working on the clutches yourself. You only need a few specialized tools, holders and pullers.

This photo shows a UTV with the clutch cover removed. The belt and sheaves look good, but there is dirt everywhere in the belt case and clutches. As you might expect, some clutches are easier to reach and service than others, but that shouldn’t deter owners from cleaning and inspecting their clutches on a regular basis.

This is a CVT case with both clutches removed. The shaft on the left delivers power from the engine to the primary or drive clutch. The shaft on the right is the input shaft to the transmission. The driven clutch mounts on this shaft.

This part is called a helix. The cutouts in the helix control upshifting, back shifting and engine braking. This one is a sad example showing wear on the surfaces and rust. Water should not be in a CVT belt case, and certainly not enough to start rusting the parts.

Mathews said, “If you ever see a crack starting on a clutch sheave (typically on the drive clutch where the shaft and the sheave meet), you should stop driving it immediately and replace the clutch. Even a small crack will end in a broken clutch. While cracks in sheaves are not common, it is something to watch for. If it breaks at high rpm, usually it will fly into the driven clutch with enough force to damage the driven beyond repair, not to mention tearing up the clutch cover.” He recommends doing this inspection at least annually, depending on use. This sheave is not cracked but chips from this deteriorated spring seat have damaged the sheave surface.

Another maintenance tip we would suggest is to periodically check clutch alignment. When your clutches are out of alignment, it causes the belt to rotate diagonally between the primary and secondary and wears out the belt prematurely. Most riders don’t have the tools to properly check clutch alignment so you may have to have your dealership or powersports shop check for you. SDi does sell this tool to check alignment. Inspect as many components of your clutch system as you can. You can imagine the mess and damage a drive belt can cause it comes apart. While today’s drive belts are stout, they do wear over time and eventually need to be replaced.

These are the various parts of a Starting Line Products clutch kit. It includes the helix, weights, springs and driven clutch. Reasons for going to an aftermarket kit include replacing a worn or damaged clutch, added performance or a combination of both. This clutch uses rollers instead of slide blocks. Matt Hasara isn’t a believer in clutch kits, but Jerry Mathews does. Hasara points out that higher spring rates and lighter rollers or weights might give you some seat of the pants feel and rpm, but they can produce less side pressure and cause the belt to slip, wearing out clutches and belts. “Would you rather use clutch components designed in a million-dollar testing facility by powersports manufacturer engineers or by some guys making stuff to put in the clutch?” He continues, “Don’t get me wrong, some clutch kits work, but do your research and find what is right for your machine. Often it is the good old stock setup.” Mathews is convinced that machines with engine mods, added weight or larger tires are genuine candidates for clutch modifications. A quality clutch kit will bring back response lost to taller, heavier tires.

DO SWEAT THE SMALL STUFF

There are a few “little” things Mathews pointed out that deserve attention while cleaning and inspecting CVT clutches. When reinstalling the clutch cover, ensure that the seal is in place. Failure to do so can allow water into the clutch cover during creek crossings. This will result in belt slippage, premature wear and clutch failure. There is a drain plug in the bottom of most clutch covers. If you suspect you have water in your cover, pull the plug and drain it. Let the clutches dry or pull the clutch cover and dry the clutches and the cover. Even a small amount of moisture on the clutches can cause them to slip on the belt. That creates lots of heat and damages the belt and clutches.

Carry a spare belt, the tools to change it and bone up on the knowledge to perform the task quickly in the field. Should you blow a belt, make sure to clean all the belt pieces out of both clutches and the clutch cover exhaust duct. Check behind the clutches to make sure there are no belt strings wrapped around the PTO end of the crankshaft or the input shaft of the transmission.

Clean the belt tracks off the sheaves of the clutches with a maroon Scotch-Brite pad. Use light, equal pressure and keep from sanding in just one area. Scuff up both sheaves in a cross-hatch pattern to remove the glazing (polished surface) from the clutch sheaves and provide better traction for the belt and better performance.

Performing the proper maintenance will substantially increase the life of your clutches and provide many miles of trouble-free use.