· Coop 1, or the shim mod.
The addition of shims to the front clutch collar. Very thoroughly described in Tech Tip CVT mod (Coop45 mod) - 700/750
This mod when using the full 2MM of shim, reduces the operating ratio of the CVT evenly across the range by @5%, virtually restoring stock gear ratio on a machine that has been fitted with 26" tires over the stock 25".
This is a remarkably inexpensive mod and holds the best bang for the buck for anyone looking to hop up his King and who is not afraid to do some minor monkey wrenching that is barely more involved than changing the belt.
The compromise is that the belt will now describe a tighter circle in the front clutch than it did. This does not seem to be any problem with the stock Suzuki belt or with belts of similar construction like the Carlisle UA837 but may shorten the life of belts with a thicker section such as the Dayco HP2234. (search for 'Bang' for further info)
Another thing to consider is that the shim mod causes the splined fixed plate to ride further out on the wet clutch output shaft splines and there is not an abundance of that shaft splines to start with! Due to manufacturing tolerance differences in different machines some owners find that they do not have a safe margin of spline left to engage the fixed plate when using the full 2MM of shim mod, and they have to back it off to 1.5MM or 1MM total shimming.
Owners doing this mod that have stock 25" tires will see their top speed reduced by 5% though the quads low speed technical 'rock picking' ability will be much better.
Owners with 26" tires will have about the same top speed as they had with their stock 25" tires though the speedometer, driven off the transmission as it is, will read slower than it did for the same ground speed.
· Coop 2, or fixed plate mod
Again very well described in the Tech Tip Clutch mod Coop45 's fixed plate mod - 700/750
This mod restores the top speed that can be lost as a result of the Coop 1 mod. The low reduction of the Coop 1 is retained and with the re-arcing of the fixed plate as shown, the moveable plate is once again pushed as far in as before when the rollers are at the outer extreme of their channels. This restores the lost 5% of top speed for people with 25" tires and a 2MM shim mod.
It can also permit higher top speed than stock for people who have fitted larger diameter tires, if their engines develop enough power to pull such gearing.
The machines speedometer cannot be considered an accurate measure for top speed when considering Coop mods and changed tire sizes. The speedometer drives off the engine transmission unit's gear train and it assumes a 25" tire. When larger tires are fitted, the real ground speed will be faster than the speedometer reads and given the fact that the different tire manufacturers do not make a consistent and reliable diameter for their tires stated size, you cannot even rely on mathematics to get a yardstick for your speed! A GPS with speed readout is about the only reliable standard to measure speed when you have modified tire size and you want to measure your results.
If tire size has been even modestly increased then a Coop 2 may not be needed along with a Coop 1, and can even be detrimental overkill if the engine is not then able to achieve top RPM and reach the rev limiter. It would then be over geared.
On the other hand if you can pull the gearing it might have long legs and enable the quad to loaf along open gravel roads at high speed for the RPM, and the quad might deliver better gas mileage under these conditions.
Once tires as big or bigger than 27" are fitted then the Coop 2 mod is definitely not the mod you want*, as the machine will never produce the power needed to pull that tall of gearing without both NoS and the help of a Bonneville style full fairing.
*...Unless you are a serious mudder and your goal is getting as high a potential wheel speed at top CVT ratio as you can get in low range, and you do not care about an overgeared top end in high range.
· Coop #3 (Standard, with seal protecting ridge)* (note: This mod is pretty much antique, machining mods have passed it by)
*There have been a few different ways of describing the #3 mods. I'll try to use a standard that I hope doesn't offend anyone.
The #3 is the moveable plate machined down to a depth of 2MM, at the same angle as supplied by Suzuki.
Zundappchef's drawing below shows two views of a stylized moveable sheave, as seen from the front of the machine, with angles and cut depths exaggerated for clarity.
The one in red marked 'Coop Mod 3' shows the clutch face turned down on an angle matching the original clutch face surface. This mod has exactly the same effect as the 2MM shim mod (Coop #1) but does not make the steel fixed plate ride further out on the wet clutch output shaft splines the way the shim mod does.
Compromise: The #3 mod reduces the gearing all across the CVT's range just like the shim mod. This may be exactly what the owner of a larger tire equipped machine wants, while owners of stock 25" tires would see their top speed as regulated by the RPM limiter reduced by 5% (on a 2MM cut sheave)
Note: There must be a seal protecting lip at the center of the plate for this mod and the #3.5 mod. See the description in the next article paragraph.
The collar on which the moveable clutch plate rides has a plain bearing equipped hard steel insert held in by its interference fit, a step in the bore on the roller side, and a retaining ring on the clutch face side.
There are seals press fitted onto both ends of the collar bore because the moveable plate rides to and fro on the collar and the plain bearings inside need the bit of grease inside that space, which must not be contaminated with belt dust nor the belt contaminated with grease. The seal on the clutch face side is basically flush with the clutch face. This means that the clutch face cannot be machined down all the way to the middle or this seal would lose most of its pocket and the belt when worn or when shims are employed as well, might go low enough to contact and dislodge it.
For this reason, when doing a Coop #3 or Coop #3 tapered mod the machinist must leave a ridge of aluminum from the old face dimension to support and protect the seal. (this pic courtesy TheGreenRider. The chipping damage isn't the focus of our attention) This pic shows the ridge needed to protect the seal.
If shims are added to the Coop #3 or coop #3 tapered there is the possibility that the belt may become notched on one side of the inner ribbing.
There should be plenty of belt clearance above this ridge for the belt of a Coop #3 modded clutch that does not have additional shims and has an in-spec belt. The apparent slight differences in tolerance among machines suggests that additional shimming with a Coop #3 or #3 tapered can result in contact. Not that this is the end of the world or that contact of the belt on a seal protecting ridge will result in failure, and no such belt failure has yet been reported due to a Coop #3 mod and shim, it's just something to be aware of.
· Coop #3 tapered (Shown as Coop 3.5 in the drawing) (note: This mod is pretty much antique, machining mods have passed it by)
The sheave is machined as in the Coop #3 but the angle of the moveable plates surface is increased so that while the innermost part of the clutch face is reduced by the previous 2MM, the outer extreme of the clutch face is not changed at all.
This retains the top gear ratio as it was when stock but reduces the lowest gear ratio by the amount of a full 2MM shim mod. The CVT is actually broadened in its operating range by this mod, and the ones that come after. A lower low is achieved and the top ratio is retained as before.
Good for 25"-26" tire equipped Kings so that top gear ratio (top speed) is retained while the lower low end is achieved.
The inner seal protecting ridge is retained as in the Coop #3.
· Coop #3 plus (Coop #3+) Tapered and straight (big tire)
A further development of the Coop sheave mod by Tonyjames28, in which the seals are removed and the inner hardened clutch bearing insert is pressed out and reduced in length by the machinists choice, 2.5 MM being prudent. This amount allows sufficient wall material for a the machinist to make a new ring groove.
The insert is then restored to its place and a new snap ring groove is cut that same distance (3 MM) inboard of the original. The seal is replaced 3 MM inboard of its old location and now the clutch face can be machined as either the Coop 3 Tapered or the Coop 3 (for bigger than 26" tire). No protecting lip is needed with a Coop 3+.
The clutch face is modified for its full inner range and only the collar itself now limits the innermost potential of the belt, depending on belt wear and the amount of shim chosen.
Compromise: As in all the mods above the belt will describe a smaller circle than stock. This may affect belt life and reduces the area of contact in which the motor's power is transferred to the belt. The belt has the least contact when it is transferring the most torque. At high throttle settings slippage can theoretically occur depending on secondary spring strength. (in practice, when making a big application of throttle the belt spends very little time at its innermost location, beyond the initial surge)
Pic courtesy of Tonyjames28
#6)
· Coop 4
This mod leaves the moveable clutch face alone and it involves machining on the roller side of the moveable clutch, to allow the rollers to travel further down their channels and the fixed plate to sit far enough into the roller side of the moveable plate to permit the advantage of this.
All of the Coop mods but for the #2 accomplish the same thing, at lowest reduction they allow the belt to drop further into the front clutch and to form a smaller pulley from it. This makes the rear clutch a larger pulley, though only by a small amount given the relative proportions of the clutches at this point.
The result is lower gearing at the low end in all cases, a desirable thing to have in the notoriously tall geared King Quad, especially the 700-750 models.
Several people who have access to machine shop tools and who are machinists or can get an adequately skilled machinist to do the work, have done one or more of these mods for themselves. As well, there are forum members who do the mods for a price including the author of this Tip, and they are readily found upon asking on the King Quad forum.
There are numerous other CVT machining mods including machining of the secondary sheaves, indexing of the secondary springs wrap preload, and shortening of the collar for increased top gearing, but these are outside the scope of this Tip.
- Fitting a clutch kit to make up for bigger tires
A 'clutch kit' doesn't change your low end gearing. The clutch kit only changes the RATE of the upshift within the CVT's existing range, by way of lighter roller weights and/or different strength or rotational preload of a different secondary spring. The lowest gearing in the range remains the lowest gearing in the range, determined by how small a pulley the front clutch forms at the mechanical limit of its excursion, and how big a pulley the rear clutch forms using the amount of belt the front clutch leaves it!
Now if the clutch kit also includes heavier strength wet clutch (centrifugal clutch) springs and those are installed, THEN it will make that wet clutch behave like a high stall speed torque converter in a hot rod automatic tranny equipped car or truck.
But making the engine rev higher (and be in a higher power output capable RPM) until the wet clutch shoes throw out and the clutch engages in order to get low end power, is a 'poor mans' or rather a poor engineers trick to get more power.
Would you ride the clutch so the engine revs higher in your pickup truck, in order to get more low end grunt?
The other problem is that those tighter wet springs delay engagement all the time, not just when you want it more low end grunt. This makes technical riding more touchy and less fun.
The only way to gear down the low end without gearing down the whole driveline is by machining techniques that include tapered front clutch plate machining, or machining to extend the rollers range of travel.
Then you get all kinds of low end reduction without sacrificing high speed gear ratio, and you can throw away those stronger wet springs.
Why would you want your clutch slipping and turning your power into heat as well as all that clutch shoe material contaminating your engine oil, when you can have that low end gearing anyway without the wet clutch slipping?
Some slip is necessary to get the quad underway from a stop, but slipping it to get low end gearing is not very efficient.