Relationship between roller weight and spring stiffness?

[premnas]

I understand that tuning a CVT is about taking the engine's power and efficiently putting it to the drive wheel, but I'm having a bit of trouble with a couple of concepts...

What effect does roller weight have on acceleration, and how does it relate to the stiffness of the clutch springs?

I know that stiffer fly clutch springs require higher rpms before they'll allow the clutch to engage (centrifugal force at work here)... But I'm having a hard time visualizing what the main drive spring is doing- I just know that it has to do with the top end "gear".

I thought I had a grasp on roller weight until I started poking around on Enviro-Moto's website and found this:

"Make sure your adjust your variator weights accordingly. when tuning your transmission the general rule is, heavier springs require heavier rollers"

I thought better accleration was acheived by using lighter weights with stiffer springs.  Now I'm just confused!

[Shaka]

The rollers have to pull the belt against the contra spring.  If the rollers are too light and the spring too stiff there is not enough mass in the rollers to overcome the spring force.  You will not get the belt into high gear and turn real high rpm's without going anywhere fast.  If the rollers are too heavy and the spring too light, it will shift into high gear too quickly and bog down.

[wordslinger]

..from my experience, with tuning my 4t cvt...there is a balance between top speed and decent take-off..

..the key is to be able to get the rpms up as quickly as possible, and transfer those horsepower generated rpms into usable torque for your rear tire to put to the asphalt...

..too light of roller wt, and your engine will rev high, but the rollers will not be able to push against the variator's ramp plate and moving drive face with enough force...a bit heavier roller will generates more force, causing the pulley halves to come together, making your belt ride higher, which creates a higher ratio between the "Drive" and "Driven" (clutch) pulleys...

[premnas]

Got it!  After reading your replies, I also watched a few more videos...  Now I understand the balance between the variator and the clutch, and the relationship between the roller weights and the springs.

With lighter rollers there is less pressure forcing the belt outward.  This means  higher rpms to get the same gear ratio.  The idea is to balance the weight of the rollers with the stiffness of the springs to keep the engine in the optimal rpm range...

Thanks!

[Shaka]

Exactly!

[wordslinger]

..it's always that.."AH-HAA!!" moment that makes it all worthwhile...


 

[premnas]

Yep, nothing like a moment of clarity!

I'm hoping my bushing and rollers (5 gram) will be here Saturday- they've been shipped, and were in Tampa, FL as of 10:38 PM yesterday.  I'm really excited about this, and can't wait to see the difference these mods make!

[premnas]

Well, my parts came in as expected, and I got them installed.  I had a little trouble getting the nut off the variator because I don't have an impact wrench, so I used a strap wrench to hold the gear that the starter engages... A minute later the nut was free.

What a difference!  There is a significant improvement in accleration, from take off all the way through top end, which is about 49 mph... this is what the speedometer reads, I have no idea how accurate it is.  Regardless, the speedo read 34 mph stock, and now reads 49 on a flat stretch.  That's a gain of 15 mph by cutting the CDI, replacing the stock variator bushing with an unrestricted one, and replacing the stock (6.5 gram?) rollers with 5 gram rollers.  I spent a total of $22.86, plus about $12.00 for the strap wrench.

And about 90% of the information I needed to do this I found on this forum... Many thanks!

[wordslinger]

...that's just too frikin' cool.....glad your day went better than mine brother...

[zombie]

Well, my parts came in as expected, and I got them installed.  I had a little trouble getting the nut off the variator because I don't have an impact wrench, so I used a strap wrench to hold the gear that the starter engages... A minute later the nut was free.

What a difference!  There is a significant improvement in accleration, from take off all the way through top end, which is about 49 mph... this is what the speedometer reads, I have no idea how accurate it is.  Regardless, the speedo read 34 mph stock, and now reads 49 on a flat stretch.  That's a gain of 15 mph by cutting the CDI, replacing the stock variator bushing with an unrestricted one, and replacing the stock (6.5 gram?) rollers with 5 gram rollers.  I spent a total of $22.86, plus about $12.00 for the strap wrench.

And about 90% of the information I needed to do this I found on this forum... Many thanks!

    Testify my brother! It's funny how a little scoot can be soooo much fun for a  grown up!

[wordslinger]

..and we got's two 12 inch wheels....

...hey, what's the next larger OD tire i could fit on this bitch....hmmm.......

[zombie]

Go up on both to keep the steering geometry.

[wordslinger]

...the riser i installed made the handling better..

..makes me wonder what another 1/2" would do...

..but that's another thread....

[premnas]

...the riser i installed made the handling better..

..makes me wonder what another 1/2" would do...

..but that's another thread....

Could you tell me a little more about the riser?  One thing about these smaller, lighter scoots is that they can get a little sketchy when you get 'em going upwards of 50 mph...  An increase in handling characteristics would certainly compliment the increase in speed!  It seems like stepping up an inch in tire size would help keep things stable at higher speeds.

[thelastkahl]

Hello all.  I am in the process of some of these same mods. I ordered 5.5 gram sliders, main 1500 torque spring, 1000 torque spring, and a set of three different strength fly springs and should be arriving this week.  I am hoping to have the same result.  I am a little worried about losing the top end speed with these stiffer springs and lighter sliders.  The stock roller weight is 6.5 gram.  I will be using the mid range stiffness springs and either 1500 or 1000 torque spring...What do you think?  Will I be losing top end speed for the better acceleration?   

 So many different combos...I am overwhelmed.  HELP!