Yamaha’s Ultramatic Transmission

Yamaha’s Ultramatic Transmission

Could it be the best CVT design ever?

By now you have heard Yamaha is offering a 10-year limited V-belt warranty on their Ultramatic-equipped ATV and UTV models. Obviously, this warranty comes with the purchase of a new 2019 and newer model year machine and is unfortunately not transferrable. Some may not understand why a company like Yamaha has such incredible faith in their own engineering as to offer a full 10 years of “insurance” to their consumers. Simply put, over the years it has proven itself to be one of the most reliable CVT designs on the market. When used as specified and designed, the Yamaha Ultramatic transmission has outlived many of its competitors and I hear stories ever so often of machines that have never had the CVT cover off yet still run strong 15 years later. I do not recommend neglecting the machine this way, but it is a pretty fascinating fact.

In this short read I wanted to go over just what makes up an Ultramatic transmission and how it works in laymen’s terms so everyone that doesn’t know can hopefully understand it a bit more. The Yamaha Ultramatic CVT has several components that all work together to make a seamless and smooth transition from a dead stop to a full-on sprint. What most see when peeking under the CVT clutch cover is the primary and secondary clutch sheaves as well as the actual belt, yet what many cannot see is the Automatic Centrifugal clutch and one-way sprag clutch hidden just inside the engine case behind the primary drive sheaves.

Cutaway image of X2 Ultramatic Transmission

The automatic centrifugal clutch (also known as a wet clutch because its bathed in the engine oil) rides on the end of the crankshaft and when you add throttle, the weighted pads on the automatic centrifugal clutch make contact within a housing that intern spins the primary drive sheaves that the belt is laying in. The belt never slips in the sheaves like the flyweight style clutch designs as the drive sheave always has a firm hold on the belt. As engine speed increases the weights or rollers in the primary drive sheave then start to slide outward and this brings the outer drive sheave in towards the fixed drive sheave halve. As this is happening the secondary or driven sheave begins to open up and the belt slides down into the sheave. This is how you get a smooth, constant as well as very linear speed increase on Yamaha products. The one-way sprag clutch provides engine braking when you let off the gas and this helps riders of any skill level to negotiate steep descents without feeling like the machine is freewheeling or out of control like some other belted transmissions.

Understanding this process of Yamaha’s Ultramatic transmission and the fact the belt never slips should give you a little better insight on why they offer such a bold warranty. No slipping means wear on the belt drops dramatically. So, could this be the best CVT clutch design? I personally think it certainly has its advantages and it has been copied by many other companies to this day and that just proves its value in the market. I have always heard that imitation is the sincerest form of flattery.

Let us not kid ourselves here though. There have been some belt failures in Yamaha products but the vast majority of mistakes I have seen have been user error. Driving a Yamaha ATV or UTV over the maximum-rated capacity or towing over the hitch-rating can begin a downward spiral of clutching issues, and history proves it. Many do not understand you cannot simply run around in high gear when carrying or hauling heavy loads, as it could be tough on internal components. Riding in areas where deep mud is an everyday situation will also be tough on belt life if precautions are not followed. Some riders/drivers will try to climb or crawl steep grades in high gear and this is bound to destroy a drive belt sooner or later. I guess what I’m trying to say is that if you are rough on your equipment and do not follow the recommended towing or hauling suggestions in your owner’s manual then you will make the machine suffer sooner or later.

We could not talk about the Yamaha Ultramatic transmission without at least mentioning a few of the aftermarket modifications riders can make to their clutching. Some will add spring and weight kits, found on www.ShopYamaha.com, to get more out of their Yamaha when increasing the size of the tires / wheelsthey have on the rig. Many have opted to “Slug” the Automatic Centrifugal clutch to get a presumed better lock in of the shoe to housing connection and claim it gives a better life to the actual shoe in the ACC. Many have developed belts for this system and claim them to be stronger or more reliable. I personally feel that the factory belt is the best option for any machine.  All of these modifications should be considered very carefully and be sure to read the list of “consumer responsibility” exclusions (especially number seven) before making any of these mods.

As for the 10-year belt warranty, there are some things you need to know but it is all fairly simple to understand. You can find more information on Yamaha’s belt warranty here: www.Yamaha10YearBelt.com

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