CVT tuning

[sideways]

My scooter has the 1e40qmb engine, totally standard. I'm looking to get better performance from my CVT.

I'm quite happy with how it launches but when it reaches 25-30km/h the CVT "shifts" right down and the engine struggles until about 60km/h where it's back up in it's proper rev range. It maxes out at 68km/h on the rev limit. At 60+ it will happily climb most hills without losing speed, under that and the speed plummets.

Basically what I want to do is slow down the shift so it maintains high revs for longer, but I don't want to loose top speed.

I understand that lighter rollers = more revs on so on but I'm not sure lighter rollers on their own would give me what I want. I'm thinking a stiffer contra spring (a 1000 rpm one) and some experimenting with rollers would get me what I want.

Would an aftermarket variator(and obvious tuning)give the results I'm after?

Thanks

Hayden

[90GTVert]

I think lighter rollers will be the easiest way to get some improvement. The rollers and the contra spring work with (really against) each other so it has pretty much the same effect using lighter rollers as it does with a stiffer contra spring. Once the belt gets to a certain point, the torque driver has to open enough to pass into it's second angle, where you feel the shift. That won't change with a different spring. You can make it take more revs to open, but it will still need to open at about the same speed to keep you accelerating. If the two systems were able to work more separately, so you could make the rear pulley work at different timings than the front, then you'd have either a belt with a lot of slack or that was too tight and snapped. So, easy answer is try lighter rollers or a stiffer contra and get the revs pre and post shift to the point that you like best.

If you want a bigger improvement I would start with an aftermarket variator. They tend to work much more smoothly. The torque driver is where that shift is really happening, but I find that with everything else dialed in the 2 angle torque driver is a good thing for a street scoot. It helps you keep the revs a little lower for cruising. Another way to really change that shift is to make more power. A street/sport type big bore kit gives you more torque and the engine doesn't struggle as bad when revs drop.

[sideways]

Mar 2, 2013 12:28:09 GMT -5 90GTVert said:

I think lighter rollers will be the easiest way to get some improvement. The rollers and the contra spring work with (really against) each other so it has pretty much the same effect using lighter rollers as it does with a stiffer contra spring. Once the belt gets to a certain point, the torque driver has to open enough to pass into it's second angle, where you feel the shift. That won't change with a different spring. You can make it take more revs to open, but it will still need to open at about the same speed to keep you accelerating. If the two systems were able to work more separately, so you could make the rear pulley work at different timings than the front, then you'd have either a belt with a lot of slack or that was too tight and snapped. So, easy answer is try lighter rollers or a stiffer contra and get the revs pre and post shift to the point that you like best.

If you want a bigger improvement I would start with an aftermarket variator. They tend to work much more smoothly. The torque driver is where that shift is really happening, but I find that with everything else dialed in the 2 angle torque driver is a good thing for a street scoot. It helps you keep the revs a little lower for cruising. Another way to really change that shift is to make more power. A street/sport type big bore kit gives you more torque and the engine doesn't struggle as bad when revs drop.

Ahh I thought the stock torque drivers had the straight slot and aftermarket ones were multi-angle. My thought was that a stiffer contra would cause the CVT to shift slower, then I could use rollers to fine tune it. Obviously that's a flawed idea with the dual angle driver.

I saw you had the KOSO variator, what did you think of it. As the cheapest, it appeals to me!

[90GTVert]

I don't think I ever had a Koso variator. I had a stock variator with a Koso ramp plate (part of a parts bundle I got on eBay). Maybe that was a Koso vari, but if so it seemed just like stock to me. I use Hoca variators from PFS for $50. Good deal IMO, but the Hoca often needs a spacer washer or two to make the drive boss long enough for best launch. You can grind down the stock washer's OD to make it work for 1mm extra. You'd also need to use 16x13 rollers or sliders instead of the stock 15x12mm, but most good variators use larger rollers/sliders.

Stock for a minarelli is a dual angle. Some other scoots do have a straight groove stock. Unless you go way too stiff or too soft you should be able to make the contra spring work with the right roller weights. I've heard of people putting in straight groove TDs and saying their rear pulley won't open all the way no matter what they try and they end up using softer contra springs. Some manufacturers include a spring when they sell a kit. So far I have been fine just adjusting weight and switching angles on the straight TDs without switching a contra spring other than to get revs where I need them in some cases.

[rupert]

"I understand that lighter rollers = more revs on so on but I'm not sure lighter rollers on their own would give me what I want. I'm thinking a stiffer contra spring (a 1000 rpm one) and some experimenting with rollers would get me what I want."

Here is what I do:
I inspect my variator (front pulley assembly) for black marks where the belt travels. If I see black marks (signs of a slipping belt) I then increase the # of the rear (take-up) spring. If I don't see black marks I leave sleeping dogs lie.

Increasing the # of the take-up spring is/can be counter productive. You have to carefully watch for the new spring for binding on the inside, and outside. If the thing binds/rubs it will NEVER work properly. If you re-assemble the take-up assembly "dirty" it will never work properly. EVERY time I get to fooling with the rear spring it seems I have to buy 3 or 4 of them to get one that fits nicely.

A "rule of thumb" is 1 gram (total roller weight) per spring #. To get the same result (everything else being equal) between a #750 (stock) and a #1000 spring you would have a 1 gram weight difference (total) in your rollers. In other words, a #750 (stock) spring combined with 3 gram rollers will behave the same as a #1000 spring and 4 gram rollers.

If I was you I would give 3.5 gram rollers (total) a shot. Your mileage WILL suffer!