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Post by scooter on Nov 29, 2014 13:45:40 GMT -5
How would you design a more reliable CVT than the ones that are common on most scooters? What do think is the weakest link in the system, the pulleys, the rollers/actuators, the belts, etc?
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Post by wheelbender6 on Nov 29, 2014 14:01:42 GMT -5
Nissan is the motor company with the most passenger car CVT experience these days. They sometimes use a belt made from several chains bonded together, rather than rubber. A paradox of the CVT, like most transmissions, is that the more durable you make them, the more power they consume (power that operates the CVT but is never transferred to the drive wheel.
-Power consumption by a CVT is not a big concern with a 200HP motor, but it becomes very noticeable on a 5-10HP motor.
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Post by oldchopperguy on Nov 30, 2014 2:29:45 GMT -5
Wow, the CVT is one part I've never had trouble with. Even on my first VERY inexpensive Chinese 150, I never had a lick of trouble with the CVT.
It's true, making the belt tougher may cost power. My China scoot had a Gates Powerlink belt, and it was still like new after six years. The clutch also seemed "bullet-proof". I'd guess the rollers would be the weakest link, but that's just me. I changed to a Prodigy variator after 3 years, and the factory rollers were pretty worn.
My current scoot, a 2007 Kymco 250 Grandvista had 14K miles on the clock when I got her last Christmas. The original belt was worn, so the dealer replaced it. The clutch, variator and rollers are still fine. I plan to go with sliders next season, because I believe they are really better at BOTH ends of the variator range; acceleration AND top-speed.
If you're having trouble with the CVT, about all I could recommend is to replace parts with the best, name-brand pieces when you fix them. They should last many years.
Wish I could be of more help...
Leo in Texas
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Post by earlwb on Dec 3, 2014 15:59:40 GMT -5
The problem with the GY6 power train is the poor air flow or cooling for the belt drive. If you improve the cooling the drive belt works fine. When they designed the GY6 type of engine setup, high speeds was not a big consideration. The scooters were made for China and at the time the roads were crowded and speeds would be typically 20 to 25 mph maybe 30 if you were lucky sometimes. So they didn't have cooling problems where the belt would heat up a fail.
Then they started selling them in the USA and everyone was running the scooters much faster. Then the CVT drive belts started overheating and wearing out fast.
Now then immediate quick fixes is to remove the little foam air filter in the CVT drive coiver. Leave the wire screen in though. That alleviates the problem as the little foam filter gets clogged up fast, maybe in 40 miles or so of riding. A longer term fix is to get a ventilated racing CVT cover and use it. The ventilated cover allows for more cooling air flow and thus the belt doesn't overheat as easily and you get much better life and mileage out of it.
The other thing is the Chinese make a lot of fake or counterfeit CVT drive belts. So you may or may not get a real brand name belt. You will have to avoid the "good deal" prices. The fake belts may not last 20 miles.
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Post by rockynv on Dec 4, 2014 8:01:18 GMT -5
The Aprilia/Piaggio bikes use a larger foam filter which you clean every 3,125 to 6,250 miles. You will get close to 50,000 miles from the variator and clutch. Belts last 12,500 to 18,000 miles. The CVT covers house an outer bearing to support the outer end of the clutch shaft which eliminates the damaging vibrations that shake apart the GY6 bikes. Modifying the filter and air inlet and better supporting the outer end of the clutch shaft would go a long way toward improving CVT reliability on a GY6.
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Post by ricardoguitars on Dec 4, 2014 8:17:41 GMT -5
Before I found this place and learned more about scooter stuff, I bought a cheap belt that got destroyed after 5 miles!! There should be a regulation that dictates all belts should be made out of Kevlar or similar material.  |
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Post by scooter on Dec 4, 2014 10:57:10 GMT -5
Before I found this place and learned more about scooter stuff, I bought a cheap belt that got destroyed after 5 miles!! There should be a regulation that dictates all belts should be made out of Kevlar or similar material. I bought two of those myself. People who sell junk like that should be ashamed of themselves. |
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Post by rockynv on Dec 4, 2014 21:27:22 GMT -5
Before I found this place and learned more about scooter stuff, I bought a cheap belt that got destroyed after 5 miles!! There should be a regulation that dictates all belts should be made out of Kevlar or similar material. A bad or cheaply made Kevlar belt can destroy your drive faces in very short order. That they put Kevlar or Aramid in does not guarantee that its a good belt. |
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Post by Jarlaxle on Dec 4, 2014 21:51:42 GMT -5
The non-Kevlar belt (Dayco, I think) in my Qlink was fine with 10,000+ miles.
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Post by JerryScript on Dec 5, 2014 0:49:58 GMT -5
The Aprilia/Piaggio bikes use a larger foam filter which you clean every 3,125 to 6,250 miles. You will get close to 50,000 miles from the variator and clutch. Belts last 12,500 to 18,000 miles. The CVT covers house an outer bearing to support the outer end of the clutch shaft which eliminates the damaging vibrations that shake apart the GY6 bikes. Modifying the filter and air inlet and better supporting the outer end of the clutch shaft would go a long way toward improving CVT reliability on a GY6. If you could attach a bearing to the end of the clutch shaft easily, a spider mesh could be added to the inside of the CVT cover for the necessary added support structure. Do you really think it makes that much of a difference? Seems an easy enough after market part to engineer, I'm surprised it hasn't been attempted, and makes me think maybe it's not that much of an issue? (not arguing, just thinking out loud) |
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Post by oldchopperguy on Dec 5, 2014 1:18:03 GMT -5
For what it's worth, I cut away the entire face of the belt-cover, exposing the clutch-bell on my old 150. I also removed the filter at the front of the cover, so fresh air (as well as water, dust, etc. had a free-flow IN and OUT of the cover). I rode it that way for 5 years, and never, EVER had any adverse effects from crud damaging the variator, belt or clutch pulley. Before that mod, the cover would get too hot to touch. Afterward, you could even touch the clutch-bell after riding!
Many, MANY modded scooters omit the entire cover, and I've yet to hear of any problems from leaving the whole CVT tranny exposed. Belt-drive motorcycles have the entire drive-belt and pulley exposed with no trouble. After a great many miles riding with the goodies exposed, I do believe the need for ANY cover over the CVT is greatly exaggerated.
The warmth from the belt friction and clutch-shoes keep the whole thing quite dry, even when rain is pouring in. The speed of the belt rounding the pulleys keeps stones and such from going through the belt and pulley. They just bounce off the spinning parts.
While ANY unusual circumstances COULD theoretically damage something, if there was much danger, the major bike-makers like Harley-Davidson just wouldn't run open belts. Some riders feel the covers keep the CVT cleaner, but at least on my old 150, the cover only served to "contain" all the belt-dust, "gumming up" the belt and pulleys... Not to mention absolutely COOKING the clutch and belt... LOL!
After opening it all up, the free-flowing air through it kept the inside of the cover quite clean and free of grit and grime.
The only conditions I'd think would require any cover at all on the variator, belt and clutch would be those where one was riding nearly 100% off-road, in pea-gravel, over stones, clods, rocks, sand, etc. VERY few scooters get THAT kind of use.
Just me, but I was VERY pleased for five years running my CVT totally open and cool. And the original factory belt and clutch were still like new when I traded "Lil' Bubba" on my Kymco 250.
Again this is just my opinion, but one formed over 5 years and around 8,000 trouble-free miles.
Leo in Texas
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Post by scooter on Dec 5, 2014 15:59:11 GMT -5
For what it's worth, I cut away the entire face of the belt-cover, exposing the clutch-bell on my old 150. I also removed the filter at the front of the cover, so fresh air (as well as water, dust, etc. had a free-flow IN and OUT of the cover). I rode it that way for 5 years, and never, EVER had any adverse effects from crud damaging the variator, belt or clutch pulley. Before that mod, the cover would get too hot to touch. Afterward, you could even touch the clutch-bell after riding!
..... Just me, but I was VERY pleased for five years running my CVT totally open and cool. And the original factory belt and clutch were still like new when I traded "Lil' Bubba" on my Kymco 250. Again this is just my opinion, but one formed over 5 years and around 8,000 trouble-free miles.Leo in Texas It's interesting that the CVTs are set up like an air filter on a carb and yet so many people ride with them open. Like your bike, my CVT case gets hot. It seems like a good mod might be to cut away most of the face of the CVT cover and then put a screen/foam/screen sandwich over the opening. That would keep out dirt and probably most water. I realize the air isn't going to flow in the way it was designed to flow, but it sounds like yours was cooling much better than stock anyway. |
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Post by rockynv on Dec 5, 2014 21:18:23 GMT -5
The Aprilia/Piaggio bikes use a larger foam filter which you clean every 3,125 to 6,250 miles. You will get close to 50,000 miles from the variator and clutch. Belts last 12,500 to 18,000 miles. The CVT covers house an outer bearing to support the outer end of the clutch shaft which eliminates the damaging vibrations that shake apart the GY6 bikes. Modifying the filter and air inlet and better supporting the outer end of the clutch shaft would go a long way toward improving CVT reliability on a GY6. If you could attach a bearing to the end of the clutch shaft easily, a spider mesh could be added to the inside of the CVT cover for the necessary added support structure. Do you really think it makes that much of a difference? Seems an easy enough after market part to engineer, I'm surprised it hasn't been attempted, and makes me think maybe it's not that much of an issue? (not arguing, just thinking out loud) People just accept that the mufflers and headers are supposed to vibrate loose. That extra support makes a big difference in how the stress is spread and takes all the deflection out of the clutch shaft. They do it on the swing arm side on the better Chinese 150's and the clutch shaft is working in about the same to less load bearing space inside the gearbox and receiving quite a bit of stress as the variator loads and pulls the clutch sheaves open. After working on both I find the Piaggio system a much more sturdy and trouble free design. Yes more work to remove the cover having to deal with the removing the nut on the clutch shaft before you can remove the cover however very much worth the effort. |
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Post by xyshannen on Dec 7, 2014 10:57:44 GMT -5
For what it's worth, I cut away the entire face of the belt-cover, exposing the clutch-bell on my old 150. I also removed the filter at the front of the cover, so fresh air (as well as water, dust, etc. had a free-flow IN and OUT of the cover). I rode it that way for 5 years, and never, EVER had any adverse effects from crud damaging the variator, belt or clutch pulley. Before that mod, the cover would get too hot to touch. Afterward, you could even touch the clutch-bell after riding!
Many, MANY modded scooters omit the entire cover, and I've yet to hear of any problems from leaving the whole CVT tranny exposed. Belt-drive motorcycles have the entire drive-belt and pulley exposed with no trouble. After a great many miles riding with the goodies exposed, I do believe the need for ANY cover over the CVT is greatly exaggerated. The warmth from the belt friction and clutch-shoes keep the whole thing quite dry, even when rain is pouring in. The speed of the belt rounding the pulleys keeps stones and such from going through the belt and pulley. They just bounce off the spinning parts. While ANY unusual circumstances COULD theoretically damage something, if there was much danger, the major bike-makers like Harley-Davidson just wouldn't run open belts. Some riders feel the covers keep the CVT cleaner, but at least on my old 150, the cover only served to "contain" all the belt-dust, "gumming up" the belt and pulleys... Not to mention absolutely COOKING the clutch and belt... LOL! After opening it all up, the free-flowing air through it kept the inside of the cover quite clean and free of grit and grime. The only conditions I'd think would require any cover at all on the variator, belt and clutch would be those where one was riding nearly 100% off-road, in pea-gravel, over stones, clods, rocks, sand, etc. VERY few scooters get THAT kind of use. Just me, but I was VERY pleased for five years running my CVT totally open and cool. And the original factory belt and clutch were still like new when I traded "Lil' Bubba" on my Kymco 250. Again this is just my opinion, but one formed over 5 years and around 8,000 trouble-free miles.Leo in Texas This is why I did this to my CVT cover. i1287.photobucket.com/albums/a624/xyshannen1/cvt1_zpsf2b6c6ae.jpgi1287.photobucket.com/albums/a624/xyshannen1/cvy2_zps155927f4.jpgi1287.photobucket.com/albums/a624/xyshannen1/cvt3_zps6e3057da.jpgI noticed that even with the motor in stock form, hauling my 200lbs rear caused my cvt to run hot. Add to that the pain of taking the cover off every time I wanted to tune the cvt, I elected to just cut the cover off. I cleaned the edges with a hand grinder and put it on the bike to give the cvt a more finished look than just not having any cover at all. It runs great and stays cool. |
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Post by oldchopperguy on Dec 7, 2014 15:41:15 GMT -5
Xyshannen,
Nice job! Have a bone!
A great many riders do similar mods with good success. I do think that opening up the CVT to fresh air adds MUCH more life to the components, negating any adverse effects. I never experienced ANY problem from water in there, and the chance of a stone or foreign matter damaging something seems far more remote than premature failures due to constant heat cooking the parts.
You've done some mighty neat stuff to your scoot! It's refreshing to see an "Italian-turtle-deck" style scoot hot-rodded. It reminds me of the old days when we'd tweak an old Vespa or Lambretta... And, like they're STILL doing in Europe!
Keep it up...
And, ride safe!
Leo in Texas
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