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Lots of people want to either give there machine more power, compensate for larger tires, or just custom tune their machine to fit their needs. This thread will explain just that, along with some basic information on how your CVT works. If there are any errors or things you would like to add or see added, feel free to pm me or send a reply on this thread. All information on this thread is from hours of research learning about the Yamaha and Suzuki CVT.

The CVT of your quad is the system that manipulates your power to climb a steep hill, go faster, or play around in the mud. CVT stands for continuously variable transmission. What it does is shift gears for you, just like a semi automatic quad does when you shift the gears. The lower gear gives more pulling power, the higher gear gives more speed. The difference with the CVT is it decides what gear to be in for you and does so smoothly. Although gears are not involved, I find it easier to consider how the CVT works using the same concept as gears.

The main goal of the CVT is to be in the lowest gear when you need it and the highest gear when you want to go fast. It does this through 2 sets of sheaves, the primary and secondary. Each set has a moveable sheave and a fixed sheave. The primary is connected to your engine and the secondary is what gives power to the wheels. These two sheaves are connected by a belt and have two sheaves in each and have tapered faces which the belt rides on. The primary is designed to start with the belt at the lowest point possible and the secondary at the highest point possible, giving you the lowest starting gear, the same as being in first gear on any semi automatic quad.

The way the quad gears up is from the weights in the primary. When the rpm increases the weights get flung out and push the moveable face further in forcing the belt to rise on the primary and go down on the secondary to slowly gear up. Heavier weights get flung out with more force than lighter weights, causing your quad to gear up faster. Commonly lighter weights will be used to give higher rpms and are better for mudding.

Now you know that the weights cause the primary to gear up, you are probably wondering what makes the quad stay in a lower gear when climbing a hill or going through deep mud. This all happens in the secondary thanks to a spring that forces the secondary sheaves together. This spring is what gives you the lowest starting point possible and keeps you from gearing up when you need the most torque possible. This spring pushes the two sheaves together and when there is resistance from the tires it pushes the sheaves together harder, forcing the CVT to gear down even though the weights are trying to gear up. This always gives your quad the proper balance of power no matter the situation.

Now that you have a basic understanding of how the CVT works, we can go on to say what modifications you can do to it and why you would want to do those modifications.

Shims: This lowers your gearing range entirely. It spaces your primary sheaves apart allowing the belt to ride lower in the primary and higher in the secondary. The reason you would want to do this mod would be to give more low end pulling power, such as a situation where you want to prepare your quad for the mud and have huge tires on it. This mod would give you the power to make up for the loss with bigger tires and maybe even more. Most quads cannot handle more than 2mm worth of shim so anything from 0.5mm to 2mm will give good gains. I noticed a large improvement from just testing 0.5mm, so don’t be afraid to add just a small shim to try it out. Remember that you will lose top speed with this mod. There are lots of videos you can find on how to do this and many write ups on it also. Part numbers are 90201-222FO for 0.5mm and 90201-225A4 for 1mm and you can get these at any Yamaha dealer.

Sheave machining: This basically does the same thing as the shim mod without the top end loss. With some sheaves you can get the sheave machined and then add shims for even lower gearing. There are many people who can machine your sheave. Although more costly then shims, it will be worth it if you want to keep your top speed.

Lighter weights: Most clutch kits contain these in them. The lighter weights will improved throttle response by making your quad take longer to gear up and will at the same time make your quad rev higher. This will cause worse gas mileage and could cause a small top speed loss if the weights are to light to fully squeeze the primary together. I have heard of drilling holes in the weights so that would be worth a try if you can’t find them anywhere else. You can probably buy the weights from a smaller model at a Suzuki dealer or from EPI, sorry I don’t have much information. Going to have to do your research on this one.

Secondary spring: Most clutch kits will also contain a stiffer secondary spring. This gives better belt grab meaning that if you are using big heavy tires, you have less chance of a slipping belt. At the same time, this will also have the same effect as lighter weights just to a much smaller extent. EPI seems to have a few springs, but not many. Once again I am not too sure where to get these for the Suzuki’s.

Wet clutch springs: Some clutch kits contain 500rpm stall springs. What these do is make your engine wind up before takeoff getting you into power faster. Good for wheelies as they give that jump before takeoff.

Fixed plate mod: To gain top speed in general or to gain it back from shims, you can have your fixed plate bent in to raise your max speed without raising your gearing. Handy if you used a machined sheave and shims together as then you can have maximum low end along with stock top speed.

That is just about all there is to it. There are many more things to learn about the clutch and more mods you can do to it, but these are the simplest ones that I know about. Any questions or things you want to add on feel free to make a reply here and ask.
 

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I'm new to forum. I'm planning on buying my first Quad it's a '07 Suzuki LTR 450 how do I know if it's a Manuel or automatic? Also I wanted to know if someone could tell me what I need to buy if I wanted to converted to an automatic and what the total price would be.
 

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That would be a full manual I believe, so it would have a clutch you need to use to shift gears. Automatics are usually 4x4 utility quads while sport quads are usually. either a semi automatic or manual.

I cant really help you on converting it to an automatic, seems like it would be a lengthy difficult process. Id say you are probably better off just getting a quad that is already an automatic. If you dont want the manual type, you may want to just get a full out utility quad. If I remember right that is more of a quad for the track, not trail riding or for use around the house. Changing it to a fully automatic could just mess with the performance of it and ruin what its made for.

Your best bet for any of these questions would be to make a new thread in one of the other sections, for this I would try just the performance modifications category (right where you found this thread) and you should get a better response there. Good luck!
 

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Good write up Matt. I want my LTA450 to be able to climb long steep hills better with a heavy load. I want shims and lighter weights right?
 

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Thanks :) Shims will definitely help for you, the 450 is already geared high from the factory so I would go with 1.5mm shim for sure. Lighter weights are mainly for the 750s and such, as the 450 already would have as light of weights as you can get. A stronger secondary spring would be a good bet just to ensure the belt doesn't slip after adding the shims and it'll help a good bit for those hills, giving practically the same effect as the weights would
 

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Perfect and I appreciate the advice. I'm new to the belt drive rigs (on big boy machines at least) and still trying to embrace the concept. I've had the 450 about a year now and have found myself wishing for all gear drive on occasion.
 

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Yep the shims are pretty universal throughout the models. Either from the Yamaha dealer or the ones through ebay will work
 

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tried putting 2mm of shims in clutch today but didnt have enough clearance. i ended up using just 1 shim but really didnt notice much of a difference speed wise. at 100, 200, and 300 feet my speeds where the same as without it. i will try adding .5mm shim on monday if its in stock at the dealer. i was able to pull the front wheels up in low gear to the point i could of flipped it over but i never tried this before the shim.
 

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You're not going to notice a 'difference is speed' in the mid CVT range with a shimmed or machined clutch, that's not what it does. It lowers the speed relative to motor RPM at very slow speeds so that you have more starting torque (less clutch slip) and more control. If it's just shimming you are doing then you won't notice speed until you try a full throttle top speed run, when if you have 2 MM shim you notice you are going around 10% slower at the time the motor runs out of breath.
Mind you if you have fitted 26" tires you will top out at the same speed as before, though the speedometer will read that much slower for the same ground speed because the speedometer drives off the gear train.
With a machining mod done right the top speed will be unchanged and the low speed will be @ 25-30% slower for the same motor RPM, making low speed technical riding much more comfortable and enabling you to do a lot more in high range that you used to gear down to low to do.
 

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can anybody out there explain to me what its for??
A clutch mod is used to help regain low end power loss. It's primary use is after people put bigger tires on in their atv. Doing this mod changes how quick the clutch engages on the belt.


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Ok after much reading here and other forums I have a pretty good grasp of how the CVT works.
I know EPI sells stronger wet clutch springs to delay lock up.
I'm curious if anyone has tried lighter springs or adding weights to force the wet clutch to lock up sooner at a lower rpm. Seems to me this would work better for "tractoring" around or rock climbing where the speed is lower. Or would it overload the motor too soon causing it to bog down?
 

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Hi Matt, Great writeup. A couple of questions if you don't mind. I have an '07 King Quad 450. The Primary Sheave and the rollers have bee machined by Coop45 and the results are impressive. Per Coop45, I also replaced the standard secondary spring with an EPI Natural. But you know the saying, more is better. Will adding a shim give me any more in the low end than what I already have, and what kind of top end sacrifice are we looking at. Thanks.
 

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I'm new to forum. I'm planning on buying my first Quad it's a '07 Suzuki LTR 450 how do I know if it's a Manuel or automatic? Also I wanted to know if someone could tell me what I need to buy if I wanted to converted to an automatic and what the total price would be.


I googled it, looks like a racer, probably manual


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hey I am new here wanting to know if I can swap a ltf 300x shoe centrifugal and put on to my ltf 230g will this do anything in performance to stock ltf 230g and is it possible?? also would it be possible to swap the 280cc block but use 230cc head and use sub trans from ltf230 to switch from 2wd to 4wd from 280cc block instead of hi and low from 230cc sub trans?
 
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