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Most of my riding is rocky/bumpy trails in the mountains of New Mexico. Elevation is between 4,000-8,000 ft.
I tend to ride around 15-20 MPH. I installed 1.5mm shims to lower the powerband for slow climbing. I would like the ATV to "upshift" sooner to lower the RPMs for quiet cruising. I don't care about power loss due to gearing. If my understanding of the CVT mechanism is correct, I would want to install heavier weights to allow the primary clutch to squeeze together sooner to accomplish this.

Two questions:
1. Is my thinking on this correct?
2. If "yes" to above, what weights would you suggest?

2012 Grizzly 550
1.5mm shims
2006 Polaris Sportsman X2 rear shocks (much improved ride)
swaybar delete
25" SwampWitch tires
 

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If you run your speed up past your cruising speed say 5 mph then back down it will backshift faster and to a little bit lower RPM. free
A stronger spring would help do this.$

Heavier weights will do what you want. Try using some 700 weights.They are around 21g. $$
 

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Question???
Does a stronger spring retard weight movement or is it a weaker spring?
 

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Question???
Does a stronger spring retard weight movement or is it a weaker spring?
I caught that last night.
I/we are always talking of adding a heavier springs. Typed heavier out of habit, sorry.
A weaker spring will let the CVT shift out faster.
 

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Stock weights are two pieces, the weight and the cover.
550 weights are 14 gr and with the cover total 16 grams.
660 weights are 16 gr. and with the cover total 18 grams.
700 weights are 18 gr. and with the cover total 20 grams.
F.Y.I. - There can be slight variances in weight of the weights. I have two sets of 700 weights, one weighs 20 grams and the other weighs 21 grams with the same cover switched between weights. Others have reported an actual total weight in the middle.

The covers and weights can be bought separately so allow for the cover weight if needed.
2 grams makes a noticeable difference, especially going down in weight for increased engine rpm at low speed. For my current set-up a 2 gram increase made a difference but 3 grams made the fine tuning dead on for what I wanted.
I concentrate on the percentage change based on the stock number.
 

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Stock weights are two pieces, the weight and the cover.
550 weights are 14 gr and with the cover total 16 grams.
660 weights are 16 gr. and with the cover total 18 grams.
700 weights are 18 gr. and with the cover total 20 grams.
F.Y.I. - There can be slight variances in weight of the weights. I have two sets of 700 weights, one weighs 20 grams and the other weighs 21 grams with the same cover switched between weights. Others have reported an actual total weight in the middle.

The covers and weights can be bought separately so allow for the cover weight if needed.
2 grams makes a noticeable difference, especially going down in weight for increased engine rpm at low speed. For my current set-up a 2 gram increase made a difference but 3 grams made the fine tuning dead on for what I wanted.
I concentrate on the percentage change based on the stock number.

So if I ended up putting 16g weights on a 550, itll hit it more low end torque which I'd need to turn 27s correct? Or should I go w a heavier weight by a gram or 2?
 

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First of all, the stock 550 weight plus cover totals 16 gr. and there are 8 of them.
There are couple things to understand about what the weight(s) do and how they do it. This is important for knowing what result to expect when going up or down in the weight of the weight(s).
At take-off (standing start), all weights are rest near the center of axis on the primary shaft and stay there until the primary turns fast enough for them to react to centrifugal force and move out. With a stock C.V.T. ratio, once the wet clutch engages the engine can apply whatever force is produced, at that engine rpm, to turn the pulley. This is in the engine rpm range where torque is the main power produced. Torque gets the grizz moving and as the engine speed increases, so the turning speed of the primary increases to impart more rotational force to the weights for them to overcome the belt tension and move out in the weight channels.
Littler weight require more engine rpm to react and heavier weights require less engine rpm's to react.
With the stock tires the weights are engineered for that drag to the system, so the taller tires increase that drag and bog down the take-off rate.

The easiest/best(in my opinion)/least expensive way to overcome the additional drag to the system is to raise the pulley ratio.

Raising the pulley ratio magnifies/multiplies the torque produced for a give rpm, and this is very important at the hit of the throttle to get the system turning. I think of it like this. A longer bar under the rock increases the leverage (torque) but a thicker bar under the rock does not.

Most that are new to C.V.T. mods start with shimming the primary first. Its easy with a few tools and reversible and costs just a few bucks. Once they get a good understanding of how the different parts of the system work together they can move on to machining.
Shimming has a limit for raising the ratio, so machining the primary face and combining shim with the machining will produce a higher ratio than shimming alone.

The higher ratio will get the grizz off the line much better, but this will cause the belt to slip in most cases. This is due to the increased pull on the belt that the stock system is not designed for. A heavier secondary spring adds more pressure to the belt to stop the slip.

In my case, once I got this work done I cut the cam plate to change the timing (up-shift) for what engine rpm the weights influenced the forward bite of my grizz. With the stock weights and the high ratio the tires broke loss and the engine hit a high rpm and the pull topped out quickly.

I tried lighter weights and the engine went from idle to screaming with the tires spinning. It would climb anything there was enough traction to climb, but the mpg dropped by half and the top speed was cut by a 1/3. That doesn't work in my area, it was very uncomfortable.

I can't write the exact specifics, but the weight of the weights is a critical component of a system named Continuously Variable Transmission.
https://en.wikipedia.org/wiki/Continuously_variable_transmission

By reading the first 3 paragraphs of the attached article, find the ratio can be changed to affect torque. I, and many others, change the weights too. Once I found my engines sweet spot for pulling, I added heavier weights to keep it there longer.

The ratio is what changed how the grizz jumps off the line, and the different weights keep the engine in the spot for best performance in my area.
 
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First of all, the stock 550 weight plus cover totals 16 gr. and there are 8 of them.

There are couple things to understand about what the weight(s) do and how they do it. This is important for knowing what result to expect when going up or down in the weight of the weight(s).

At take-off (standing start), all weights are rest near the center of axis on the primary shaft and stay there until the primary turns fast enough for them to react to centrifugal force and move out. With a stock C.V.T. ratio, once the wet clutch engages the engine can apply whatever force is produced, at that engine rpm, to turn the pulley. This is in the engine rpm range where torque is the main power produced. Torque gets the grizz moving and as the engine speed increases, so the turning speed of the primary increases to impart more rotational force to the weights for them to overcome the belt tension and move out in the weight channels.

Littler weight require more engine rpm to react and heavier weights require less engine rpm's to react.

With the stock tires the weights are engineered for that drag to the system, so the taller tires increase that drag and bog down the take-off rate.



The easiest/best(in my opinion)/least expensive way to overcome the additional drag to the system is to raise the pulley ratio.



Raising the pulley ratio magnifies/multiplies the torque produced for a give rpm, and this is very important at the hit of the throttle to get the system turning. I think of it like this. A longer bar under the rock increases the leverage (torque) but a thicker bar under the rock does not.



Most that are new to C.V.T. mods start with shimming the primary first. Its easy with a few tools and reversible and costs just a few bucks. Once they get a good understanding of how the different parts of the system work together they can move on to machining.

Shimming has a limit for raising the ratio, so machining the primary face and combining shim with the machining will produce a higher ratio than shimming alone.



The higher ratio will get the grizz off the line much better, but this will cause the belt to slip in most cases. This is due to the increased pull on the belt that the stock system is not designed for. A heavier secondary spring adds more pressure to the belt to stop the slip.



In my case, once I got this work done I cut the cam plate to change the timing (up-shift) for what engine rpm the weights influenced the forward bite of my grizz. With the stock weights and the high ratio the tires broke loss and the engine hit a high rpm and the pull topped out quickly.



I tried lighter weights and the engine went from idle to screaming with the tires spinning. It would climb anything there was enough traction to climb, but the mpg dropped by half and the top speed was cut by a 1/3. That doesn't work in my area, it was very uncomfortable.



I can't write the exact specifics, but the weight of the weights is a critical component of a system named Continuously Variable Transmission.

https://en.wikipedia.org/wiki/Continuously_variable_transmission



By reading the first 3 paragraphs of the attached article, find the ratio can be changed to affect torque. I, and many others, change the weights too. Once I found my engines sweet spot for pulling, I added heavier weights to keep it there longer.



The ratio is what changed how the grizz jumps off the line, and the different weights keep the engine in the spot for best performance in my area.

Thanks for the lesson but I knew how a centrifugal clutch works. I just put new greaseless weights and a spring in my 660. Now we're doing one in my buddies 550 and wanted to know if I should get lighter (14g) weights or heavier (18g) weights in for better power w the bigger 27" tires he put on it.
 

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If you read that you would know lowering the ratio is what you need.

Start with a shim, but on my 550 i did a lot of machining before I was happy with the torque. By the time the ratio is lowered the stock weights are good for where the 550 makes power. The problem I found with the 550 & true to size heavier 27's is starting out (where lowering the ratio comes in) once it's moving they do well.

Take off they bog and heavier weights will make it worse unless you lower the ratio. Lighter weights will only make it rev higher after it bogs on take off, and after you really need the torque.
 

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Hey Whiskey, isn't that raising the ratio?
 

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Numerically higher yes. I get backwards sometimes, used to thinking of lower gearing I suppose:peace:
 
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