KymcoForum.com
Scooters - 50cc => Agility 50 => Topic started by: premnas on June 04, 2010, 03:27:54 AM
-
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!
-
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.
-
..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...
-
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!
-
Exactly! ;)
-
..it's always that.."AH-HAA!!" moment that makes it all worthwhile...
;D
-
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!
-
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!
-
...that's just too frikin' cool.....glad your day went better than mine brother...
-
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!
-
..and we got's two 12 inch wheels....
...hey, what's the next larger OD tire i could fit on this bitch....hmmm.......
-
Go up on both to keep the steering geometry.
-
...the riser i installed made the handling better..
..makes me wonder what another 1/2" would do...
..but that's another thread....
-
...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.
-
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!
-
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!
I haven't even made any changes to the clutch springs and am still happy with the results- good acceleration and top speed of about 49 mph (according to the speedo anyway, but still a 15 mph gain over stock). Since you're going to have springs of varying stiffness, including the stock springs, you'll have plenty of options to tweak your scooter just the way you want it. I'd replace the stock rollers, and see how they work with the stock springs... Then start with the lighter springs, working your way up until you either maximize performance, or reach the point of diminishing returns. If you don't mind, let us know what springs you decide to use and what the results were using the springs you don't use. Good luck!
-
Yeah I will def post the results.
-
The best advice thelastkahl is to change one part out at a time. Then you KNOW what each one did. For the riser bit... I added 4" longer laid down mounted shocks on a MX bike. It added 2 1/2" to the seat height, and swing arm travel, which is what I wanted. It increased the attack angle of the forks by approx. 2 degrees. The bike felt GREAT. I ran it for 2-3 weeks, and was happy as a pig. RACE DAY... The track was full of standing water. I started out on my practice laps. The first full bore run I took, I landed a double/ the front tire caught the mud , and a high speed wobble of the bars put me over the top. When I woke up from my center track nap there were too many injuries to list here. The problem was I had hit the limit of stability in the geometry of the steering. The weight of resistance of the water was enough to yank the bars, and kinetic energy took over from there. My point is this... It may feel GREAT when you test ride. but there are too many variables to be sure you have your geometry dialed in. There is a margin for error built into the design on your scoot, but there is also a point of NO return. Have you seen a shopping cart wheel that wobbles back and forth at speed. The SAME principal applies here. There is no getting out of it. Sooooo BE CAREFUL when changing the attack angle. UNLESS you have a dope for a test pilot.
-
Could you tell me a little more about the riser?
..here are a cpl pics of the riser...
..for me, this design is tried and true..
..raises the seat 1.5 inches...
-
I ordered 5.5 gram sliders,
..you won't lose any top speed due to these rollers...
..i'd put my money on a 5gr roller--1000 contra--1000 fly clutch setup...
-
Could you tell me a little more about the riser?
..here are a cpl pics of the riser...
..for me, this design is tried and true..
..raises the seat 1.5 inches...
No doubt it works! My thought is going higher may just end up w/ your a$$ being lower... Just looking out for a BRO!
-
I THINK RISERS WILL GIVE YOU JUST HEIGHT BUT YOU WILL LOOSE STABILITY AT SPEEDS AND WILL ALSO GIVE YOU AN EXTRA 1 1/2 INCH MORE OF GROUND FORCE WHEN YOU HIT IT :(
-
AN EXTRA 1 1/2 INCH MORE OF GROUND FORCE WHEN YOU HIT IT Well put!
-
..all i KNOW...is that i could tell the differencce the first time i rode it, and it handles BETTER than without the riser...
..slow fast wet dry...whatever...
;D
..dumping the scoot at 45 mph is gonna hurt, from any height...
-
Any time you raise the rear you are making the front end quicker. The larger rear tire did it for me. I wanted to try going another 1/2" but I just don't trust the frame enough. Yours is a whole nuther story.