The last time I lost a CVT belt I was driving a RZR Turbo at Sand Mountain, NV. I had just come out of a large bowl (cleverly named the Super Bowl) and started down the hill when the RZR lost power and coasted to a stop.
As soon as I smelled the burning rubber I knew what happened. After turning off the engine and opening the clutch cover I found dozens of small rubber chunks and pieces of string from inside the belt. The CVT drive belt had come apart catastrophically.
Thankfully changing the belt isn’t difficult. But digging all the belt pieces out of the clutch area and CVT exhaust tube isn’t fun. Especially when everything is nice and hot from riding in the dunes all day.
The CVT (continuously variable transmission) belt is arguably one of the most important parts on a Side-by-Side. Without it your vehicle wont move. This is because the CVT belt is what connects the primary clutch on the engine to the secondary clutch on the transmission. When this belt breaks there is no longer a link between the engine and transmission. With belts costing an average of $150 not only is a broken belt inconvenient, it gets expensive when they break on a regular basis.
When you think about how much power is transferred through the CVT belt, they really are amazing feats of engineering. The new Can-Am Maverick X3 X RS Turbo RR pumps out a truly impressive 195 horsepower! And all of that power is transferred from the engine to the transmission through a rubber belt.
How long should a CVT belt last?
According to Polaris, a CVT belt should many thousands of miles. This number is generally the same from other manufactures. While that is a vague estimate, it translates into a lot of trips to your favorite riding spot and means you should not have to worry about replacing a belt every couple of rides.
In a perfect world we would all get “many thousands of miles” out of our belts but that just isn’t a reality for many UTV owners. Search any UTV forum and you’ll see post after post of owners seeking answers to their belt failure woes.
There are many reasons for a belt to come apart. Next, I’ll go over some of those causes of failure and what you can do to stop it.
What are the common causes of CVT belt failure?
- Excessive heat
- Dirty or greasy clutch sheaves
- Blocked CVT intake or exhaust vents
- Belt slippage
- High resistance terrain like mud and sand
- Improper clutch adjustment
- Large, heavy tires
- Improper belt break-in
- Improper belt cool-down
- Aggressive driving style
- Clutch misalignment
- Excessive belt travel
How to prevent CVT belt failure
Heat is the number one cause of belt failure. With almost all of the causes of failure mentioned above, heat is what actually makes the belt break.
Large heavy tires by them selves don’t damage the belt, it’s the increased load placed on the CVT components and belt that generates more heat that eventually breaks down the belt. The same goes for dirt or grease on the clutch surfaces (sheaves). The sheaves can’t grip the belt firmly and therefore excessive heat and wear occur.
The first step in cooling down the belt is getting a belt temperature gauge to determine how hot your belt is getting and in what conditions is it getting too hot. The temperature at which belt failure occurs is around 235°F.
After monitoring the temperature there are several ways to improve cooling. This is done by increasing airflow to the clutches and belt. If your belt is breaking because it’s just getting too hot, meaning the heat isn’t caused by an air blockage or dirty clutch surfaces, adding more cool air can keep that belt alive longer.
Bikeman Performance Cyclone Primary Clutch Cover – The Bikeman Cyclone replaces the top part of the primary clutch that holds the spring down. Where the Cyclone improves on the stock cover are its fan blades that increase airflow up to 50 CFM at full shift out. This improved airflow and can keep the air moving inside the clutch housing, cooling the belt and primary clutch.
CVT Vent Scoops – Scoops to funnel more air into the vents can increase the air flow to the clutch housing. This increased airflow is a good way to keep the belt cool if it’s getting too hot due to a lack of airflow.
Inline CVT Vent Fan/Blower – If an air scoop on the vent doesn’t give your CVT enough airflow you may need an inline fan to push more air in. The fan mounts inline in the CVT intake tube to push air into the clutch housing. A common complaint with these is that they restrict airflow at high RPM.
Desertcraft CVT Blaster – The CVT Blaster is a additional intake hose with a fan for the clutch housing. Unlike an inline fan the CVT Blaster creates a second intake tube with a fan mounted to the clutch housing. That eliminates the concern of the fan restricting airflow at high RPM because the CVT system now has 2 intakes.
Desertcraft MOFLOW CVT Exhaust – Desertcraft also sells an additional exhaust outlet kit for the clutch housing. This second exhaust helps the hot air inside the clutch housing escape more efficiently, allowing the belt to stay cool.
Removing the clutch cover – Leaving the clutch cover off while riding isn’t something I would do or recommend. That said, some riders remove their clutch covers in the dunes to increase air flow to the belt and clutches. They say after doing so, they no longer blow belts. It may be true that the increased air flow greatly reduces the belt’s temperature but it also means sand is getting in your clutches. This will drastically reduce the life of the clutches … do so at your own risk.
High resistance terrain or large tires
Riding through deep, thick mud or fine, soft sand are some of the funnest terrains you can traverse. The problem with both of these is the increased load they place on the engine and clutch system. Much more stress is placed on the UTV when it goes through these conditions. The same goes for larger tires, sand tires or mud tires. Sand paddles, big mud lugs or just larger diameter tires take more power to rotate.The brunt of that stress is placed on the belt.
To prevent belt slipping (sometimes called “spin-burn” or “hour glassing”) and too much heat when stuck in sand or mud be sure to use low gear. The same goes for loading and unloading your UTV.
If low gear isn’t cutting it, a clutch kit will help belt life if you do a lot of sand or mud riding. Clutch kits reduce belt slipping by changing the stall point and shifting of the clutch. These kits are carefully designed and tested by the companies that make them to ensure the best performance for their intended application.
Proper belt break-in and cool down
When the CVT belt on your Side-by-Side does break its important to follow the proper belt break-in procedure after installing a new belt. Putting a new belt on and riding hard will shorten its life. When a new belt is installed it needs to wear in and mate to the faces. This ensures optimal grip.
According to EPI Performance the first step for breaking in a new belt is to wash it with soap and water. This removes any leftover materials from the manufacturing process. Belts may have a release agent that can cause it to slip if not washed off before use.
Next, clean the clutch sheaves (faces) with a Scotch-Brite pad or fine sand paper. This lightly roughs up the clutch surfaces so the belt can seat correctly. Use brake cleaner to remove any reside after cleaning the faces.
After prepping the belt and clutches it’s time for the actual break-in. Drive for 20 miles of easy riding. No hard acceleration, no full throttle operation and no high speed driving for an extended period of time. Take frequent breaks to allow the belt to cool down. Use low range for steep hills or technical terrain.
Polaris mentions a similar procedure for breaking in a CVT belt. Their process involves using low range for 5-10 miles while varying engine speed and staying below full throttle.
If you don’t use low range, vary the engine speed for 50 miles while keeping it under full throttle.
According to Polaris, “Breaking in a belt is about more than a set number of miles and avoiding high engine RPM. It’s about flexing the belt in the correct direction. The side faces need to wear and mate to the proper angle of the sheaves and wear into the correct friction … The goal of break-in is to achieve a high number of flex cycles under low load while maintaining low temperatures.”
Allowing the belt to cool down correctly is equally important to a proper break-in. If you have been working the machine hard don’t stop the vehicle and turn it off when the belt is still hot. Drive it easy for a few miles before shutting it off. This applies to any time you are riding, not just during the break-in period.
On our RZR Turbo we found the best way to cool the belt fast after getting it really hot in the dunes was to stop, put it in Park and rev it to about 4,000 rpm for a bit. The temperature quickly dropped according to our Razorback temperature gauge. It seems the air flow from the spinning primary clutch does a great job at cooling the belt when you are stopped and at a high enough rpm.
Adjust your driving style
It’s possible there’s nothing wrong with the clutches or belt on your UTV. The cause of your breaking belts might be your driving style. Hard acceleration on surfaces with a lot of resistance (like sand and mud) or slipping the belt in tight, technical situations is going to stress the belt. Do this enough and it will eventually break.
If you always hammer on the throttle and regularly blow belts, easy up on your driving style to make your belt last longer. Running at high speeds or wide open throttle for very long is a sure fire way to blow belts.
Another possible cause of failing belts is clutch misalignment. When the primary and secondary clutch are no longer lined up up correctly faster belt wear occurs. Misalignment can happen when the engine or transmission start to sag over time or if the engine and transmission are unbolted from each other and not correctly mated back together.
Another, but less common cause of the clutch misalignment is a bent inner clutch cover. The cover may be bent enough to cause alignment problems but not bent enough to be seen with the naked eye. To determine if the cover is bent remove the inner cover and place a straight edge on it and check for straightness.
The alignment of the primary and secondary clutch not only needs to be inline but also at the same angle. The SDI clutch alignment tool will help realign your clutches if they are out of alignment.
Excessive belt travel
This problem seems to be isolated to the Polaris RZR 1000 and RZR Turbo models operating at high speed. When belt failure is caused by excessive belt travel the primary clutch is missing a large, thin black washer called the speed limiting spacer. This spacer prevents the primary clutch from closing too far at high speed which in turn prevents the secondary clutch from opening too far. When the secondary opens too far it causes the belt to drop down to the shaft connecting the two halves of the secondary clutch. When this happens the belt rides on the clutch shaft instead of being gripped by the sheaves.
To test if this is the cause of your belt failure look at your belt and see if its worn on the teeth. If so, the bottom of the belt will be worn. This means the belt is traveling too far down the secondary clutch and riding on the shaft between the sheaves. This causes excess heat and wears away at the teeth of the belt.
Protect your belt and give it the long life your wallet deserves
As you can see there are many reasons for a belt to blow on a Side-by-Side. It could be anything from too much heat caused by a blocked CVT intake or exhaust tube to clutch misalignment or improper assembly of either the primary or secondary clutch. It may even be your driving style or the terrain you ride in is just hard on the belt.
Now you know the many causes of UTV belt failure you can perform the necessary steps to keep yours lasting for many rides.