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 Info for Yamaha CVT clutch tuning and mods.

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TCM Race Team

Joined : 2008-01-20
Posts : 1604
Age : 38
Location : moulton, alabama

PostSubject: Info for Yamaha CVT clutch tuning and mods.   Thu Sep 23, 2010 2:28 pm


1) The shim mod (Originally called the Coop45 Mod) will give you basically a gear reduction due to making the belt ride lower in the primary sheave & will make the belt ride higher on the secondary sheave.
The shim will give you more torque multiplication.
Shimming lowers your max speed a avg. 2mm shim 5mph give or take 1mm shim maybe 2-3 mph

2) Rollers
Will change the timing/shift out or how soon your atv will change gears per say.

a) Lighter rollers will stay in 1st gear longer & in which reduces bogging BUT
(its kind of like having a drag car that does excessive wheel stands--if the weight transfer from the wheel stand is not needed, then your just losing ET by forcing the car into the air instead of traveling forward.)
So if your not bogging than you donít need the lighter rollers.
Also the lighter rollers will make you engine turn more RPMs while path riding because the lighter rollers wont let the belt shift into 2nd gear or 3rd per say.
b) Heavier rollers will get you into your mid range curve sooner. Lets say that Heavier rollers will shift out of 1st gear sooner & gets you into 2nd sooner. (You get wheel speed faster to clean your tires unless your bogging then the rollers are to heavy)

3) Stiffer internal clutch springs allows a higher rpm engagement before the bike moves in which its side effect is shorted internal clutch life & more contamination of the oil.
(So internal springs depends on riders preference)

Basic Notes
PS after adding shims
(Bolt the cage on & run the motor before putting the clutch housing cover on so the belt will set in place & not rub the housing cover at start up.)

Things that alter the belt travel
Primary & secondary overall

1) Roller/weight diameter
(Larger pushes belt out farther on primary)
(May shorten inner belt travel on primary so the inner roller travel path may need to be lengthened/machined)

2) Machining the roller/weight path Mod. (Outer travel area)
(Extends the area the rollers travel to allow the faceplate to be pushed farther in which pushes the belt out farther in which increases top speed)

3) Shimming
(Belt rides lower in the primary in which increases gear multiplication/low end pull)
(Reduces the angle on the face plate, in which reduces the push on the belt to the outer rim of the primary. Reduced top end speed)

4) Machining farther down into the primary Mod. (Depth Cut)
(Belt rides lower into the primary but with no change to the faceplate angle in which increases the low-end gear multiplication)
(While machining to get the depth cut into the sheave, the angle is changed DUE to cutting for the depth)

5) Faceplate angle Mod
(Pushes the belt farther out on the primary)
(Done to increase wheel speed)
(Also done to counteract the angle loss when using the shim Mod)
(Smaller cc atvs may only notice its effect in a low range gear due to parasitic loss in the drive train or any other power robbing sources)

6) Machining farther down into the secondary Mod. (Depth Cut)
(While machining to get the depth cut into the sheave, the angle is changed DUE to cutting for the depth)

(This Mod pushes the belt farther down into the secondary in which increases speed BUT this area is run through before the face plate tops out the top of the primary)
(Maybe this mod will help counteract the shim mod issue of reducing the faceplate angle & regaining the extra push the faceplate needs to push the belt out on the primary)

Things that alter belt shifting speed.

1) Centrifugal force. (Roller weights)
Heavier rollers shift faster.
Lighter rollers shift slower.

2) Secondary spring pressure.
More, equals slower up shifting & faster down shifting.
(Less is prone to a slipping belt).

3) Sheave angles. (NOT depth angles)
(But controlled by spring pressure)
4) Face plate angle length.
a) Steeper equals faster
b) Less equals slower

5) Roller path length.
a) Shorter equals faster
b) Longer equals slower

6) Sheave surface texture
a) Ruff in which equals more friction.
Belt ware may increase due to better back shifting & tracking of the belt & the heat created due to friction.

b) Smooth in which equals less friction.
Belt ware may be reduced due to less back shifting & tracking & less heat generation.
(Spring pressure maybe more important here but of course spring pressure increases friction also)

Things that reduce horsepower in the clutch system
1) Friction.

Things that induce horsepower in the clutch system
1) Lighter parts
(Weight reducing Mod (of the Sheaves)
(This increases engine acceleration due to less parasitic loss)
(But at this extent are we really noticing it???)

In conclusion,
the belt starts at the base of the primary in which is the low-end power area.
Things that allows the belt to lower more into the primary
1) shimming.
2) Machining the primary depth.


Primary Rollers
The 350s has 6 rollers total
The 400 & larger atvs has 8 rollers total

6 roller housing
6ea x 12 = 72 total
3ea x 12 + 3ea x 14 = 78 total
3ea x 12 + 3ea x 16 = 84 total

6ea x 14 = 84 total
3ea x 12 + 3ea x 18 = 90 total
3ea x 14 + 3ea x 16 = 90 total
3ea x 12 + 3ea x 20 = 96 total
3ea x 14 + 3ea x 18 = 96 total

6ea x 16 = 96 total (stock 350)
3ea x 14 + 3ea x 20 = 102 total
3ea x 16 + 3ea x 18 = 102 total
3ea x 16 + 3ea x 20 = 108 total

6ea x 18 = 108 total
3ea x 18 + 3ea x 20 = 114 total

8 roller housing
8ea x 12 =96 total
4ea x 12 + 4ea x 14 = 104 total
4ea x 12 + 4ea x 16 = 112 total

8ea x 14 = 112 total (stock 400 & 450)
4ea x 12 + 4ea x 18 = 120 total
4ea x 14 + 4ea x 16 = 120 total
4ea x 14 + 4ea x 18 = 128 total
4ea x 12 + 4ea x 20 = 128 total

8ea x 16 = 128 total (stock 550 & 600)
4ea x 14 + 4ea x 20 = 136 total
4ea x 16 + 4ea x 18 = 136 total

8ea x 18 = 144 total (stock 660)
4ea 16 + 4ea x 20 = 144 total
4ea 18 + 4ea x 20 = 152 total

8ea x 20 = 160 total (stock 700)

Stock 07 350, 09 550 & 01 600 has 14-gram rollers, with cover =16 grams.
Yamaha roller part# 4WV-17632-00-00

Stock 07 400 & 450 has 12-gram rollers, with cover =14 grams.
Yamaha roller part# 5GH-17632-00-00

Stock 07 660 has 16-gram rollers, with cover=18 grams.
Yamaha roller part# 5KM-17632-00-00

Stock 07 700 has 18-gram rollers, with cover=20 grams.
Yamaha roller part# 3B4-17632-00-00

Yamaha Part # 90201-225A4-00 washer plate, Thickness = 1.0mm
Yamaha Part # 90201-222FO-00 washer plate, Thickness = .5mm

Other Parts
I looked over the parts lists on Yamaha's parts lists & out of the 350, 400,450 600,660, 700,
the 400 & 450 have the same clutch assembly part #s,
the only thing different between the 550 & 700 clutch assemblyís is the roller weights.

350-450 Notes
When shimming the 350 2mm you will have to leave off the retaining nut washer on the primary sheave to get enough threads for a full nut.
Also the 350 has more belt housing to secondary sheave clearance on the 350 than the 450.

When shimming the 450 2mm, the belt will rub holes into the belt cover (in the pic below). I only had 2 to rub completely through & they where the 2 on the left of this pic.
When the cover is mounted, those holes are on the bottom corner area.
I don't recommended more than 1.5mm on the 450.
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