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Old 10-07-2013, 05:48 PM   #16
JerryH OP
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Seems like they became popular in the '80s in the U.S. with Japanese scooters. Many people don't want to shift. I have a Stella with a manual transmission, and it if fun to ride for short distances, but it gets old in a hurry riding through stoplight after stoplight in town.

Many cars use CVTs, and they all seem to have short lived transmissions. I looked at the Nissan Versa and Sentra, which have CVTs, and keep hearing the transmissions fail after 30,000-40,000 miles. I was also looking at the Chevy Spark, but they changed to a CVT on it for 2014. It seems the concept has been around for a long time, but it never became popular due to reliability issues. Subaru used to sell a car called the Justy here, with a CVT, but it was considered unreliable for long distance travel (like I use my Vino for) and was designed more for city use. It appears a CVT is not the best thing for long distance riding/driving. I keep hearing about maxi scooters with a lot of highway miles on them, maybe they have a more robust setup than the smaller scooters. I also don't know how many belts they have been through.
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Old 10-07-2013, 05:48 PM   #17
k-moe
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IIRC CVT transmissons have been in scooters since the mid to late 1950's

The advanages include a lower learning curve for the rider, and better fuel economy (always being in the right gear).

Jerry, If the torque driver isn't serviced regularly the rear pully won't open smoothly, nor will it open fully at speed. As the grease ages, and dries out, it also begins to hinder movement. In addition the pins in the torque drive begin to wear into the slots, and the bore of the movable sheave begins to get out of round. The result is the variator fighting against the torque driver (more than it usually does) trying to adjust the rear pully. The belt heats up (beyond the normal amount), stretches (the total distance the belt has to turn around is lengthened when one pully isn't moving in synch with the other), and shreds. The whole proces is exacerbated by the tendency for U.S. riders to spend longer periods of time at higher speeds.

k-moe screwed with this post 10-07-2013 at 05:56 PM
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Old 10-07-2013, 06:00 PM   #18
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Well I guess I will pull the rear assembly apart and check it out, and replace any worn parts before putting it all back together. I have the service manual, but I didn't think there was anything back there besides the face of the sheaves and the clutch that could go bad.
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Old 10-07-2013, 09:05 PM   #19
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DaBears: Thanks. I learned from your post. Much appreciated.
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Old 10-07-2013, 09:58 PM   #20
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In '64 I was riding a 61 Lambretta Li150 - newfound freedom for me, cheap transportation and fun.
Here's a youtube of a similar scooter, watch his left hand, what could be easier? Before you ask, the rear brake was a footbrake.
http://www.youtube.com/watch?v=JtxMy1vLrSg
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Old 10-08-2013, 08:49 AM   #21
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Originally Posted by Dabears View Post
Trade your CV drive for a transmission and all you do is lose your belt and gain a whole new set of problems. If you want to tinker with cables and a clutch get an old Vespa. If you want reliable transportation stay with your HD200- you have a great scooter. I'm betting even JerryH will acknowledge that the belt drives are usually a reliable, and well thought out design. FYI, I have a manual Vespa and SO want and HD200......
Or a Stella, though I was talking to the local Genuine dealer this weekend and he was saying that he has folks lining up for the new automatic Stellas that are coming in. He was saying that the majority of people who come into the shop intending to buy a Stella end up not doing so because they don't want to shift. In town where scooters really shine twist and go has so many advantages with all the traffic lights, stop signs with stop/go traffic.

Personally, I like shifting cars but not living in places like San Francisco where hills combined with traffic and lots of lights/stop signs takes all the fun out of it. I didn't have m/c in San Francisco but I wouldn't want be riding a manual there either. Scooters on the other had are easy peasy in town. Heck, I've got a paddle shift option on my car but the only time I'd use it is the mountains not in Houston or Denver.
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Old 10-08-2013, 10:29 PM   #22
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Ok, I just took the entire rear pulley/clutch assembly apart, and did not find anything wrong. That thing is a PITA to work on and I had to make a couple of new tools. I didn't find anything wrong or worn, though there was not much grease. I will put some more grease when I reassemble it. The clutch looks like it has plenty of life left in it. Most of the mileage was on the highway, not stop and go. It still has the original rear brakes, and the front pads were only recently replaced. So still no clues about what happened to the belt. I would say WOT throttle riding carrying a lot of weight might be the cause, but that would not explain why the other belts did not break. Also there is a ring of rubber around the outer edge of the front pulley, where the belt would have been most of the time, but nothing on the rear pulley. That also puzzles me.

Up until now, belt drives have been totally reliable on scooters. Counting the Zuma 50, Metropolitan, Zuma 125, and Vino 125, I have nearly 50,000 miles on CVT scooters with no failures at all, so this is an oddity.

However, I have seen a lot of broken serpentine belts and timing belts on cars. You would think they would last way better, because they do not move up and down in the pulleys. Scooter belts look a lot like timing belts except for the edges, which are tapered to match the pulley.


Another thing is that this belt was torn to pieces all the way around, yet the scooter ran perfectly right up to the second it failed. It must have somehow got twisted up in the pulleys.
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Old 10-09-2013, 07:21 AM   #23
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WOT throttle riding carrying a lot of weight might be the cause
Very plausible since the variator is pretty much a heat sink for the crankshaft, and "insulated" by TWO covers on the Vino 125.



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Old 10-09-2013, 11:20 AM   #24
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Was it a Kevlar belt? I've heard that despite usually being more durable than just a rubber belt, the kevlar ones tend to shred when they go, instead of just snapping. May have just been a weak point in the belt that caused it to let go early. Probably a 1 in a 1000 occurance...
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Old 10-09-2013, 11:52 AM   #25
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Is the CVT filter even supposed to be oiled? I'd hazard a guess that a bit of excess (or unneeded?) oil from the filter either restricted the cooling airflow too much - leading to the belt overheating - and/or oil contaminated the front pulley, leading to belt slippage (leaving behind the rubber buildup on the pulley you mentioned) and thus overheating>failure.
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Old 10-09-2013, 06:39 PM   #26
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Another possability is that the belt rode too high in the variator and flipped over. Normally that happens when the weights are changed to get more top speed, without taking into account the ride height of the belt. Since you have the stock variator, and the original rollers, I doubt that is what happened.

Tortoise: The heat issue has been looked into by several people on Zumaforums.net. Yamaha did a great job of ensuring that there is sufficient airflow through the CVT case to keep the belt cool. Having said that; I did run my Zuma 125 without the outer plastic cover in order to increase airflow, and the belt temperatures did drop enough to make me want to keep that cover off. If I lived somewhere with precipitation I'd want the cover on.

ohioth: all belts tend to shred once they go. Kevlar belts have arimid fibers instead of cotton fibers, otherwise they are the same. Kevlar is better suited to dragracing (less stretch).

Moat: The CVT filter operates the same way the pre-filter on a lawnmower does. It just grabs the larger particles of crud to reduce the number of abraisives that get to the belt (belt dust is abrasive enough on it's own, so keeping road grit out is very beneficial). It's supposed to be cleaned and re-oiled regularly. A CVT belt will slip some on acceleration. The whole drive system relies on friction between the belt and pulleys, and some slippage is unavoidable.

Jerry: before putting the new belt on, mark the face of the variator with a sharpie (radially). Go on a ride (you can leave the CVT cover off for this) where you can get up to the top speed of the scooter. After the ride check the sharpie marks. There should be no less than 1/8" of the line present at the outer edge of the variator pulley. If the belt rides higher than that it is possible for the belt to jump the lip of the pully and flip (or shred).

k-moe screwed with this post 10-09-2013 at 06:48 PM
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Old 10-09-2013, 07:47 PM   #27
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Originally Posted by ohiotj View Post
Was it a Kevlar belt? I've heard that despite usually being more durable than just a rubber belt, the kevlar ones tend to shred when they go, instead of just snapping. May have just been a weak point in the belt that caused it to let go early. Probably a 1 in a 1000 occurance...
Even the OEM belts have Kevlar in them...just not as much.

The Kevlar aftermarket belts are typically considered more brittle than stock.

It's my UN-scientific belief Kevlar doesn't like heat*, and the aftermarket belts aren't as tolerant because of their higher Kevlar content....they are "performance" oriented and typically performance parts have a shorter service life. Not meant for thousands of miles of service, "off-road use only" is the typical disclaimer.

*I base this assumption on the specific warnings in ALL my Kevlar enhanced riding apparel advising air drying only, vs. heated drying.
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Old 10-09-2013, 07:50 PM   #28
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Is the CVT filter even supposed to be oiled? I'd hazard a guess that a bit of excess (or unneeded?) oil from the filter either restricted the cooling airflow too much - leading to the belt overheating - and/or oil contaminated the front pulley, leading to belt slippage (leaving behind the rubber buildup on the pulley you mentioned) and thus overheating>failure.

No, don't oil CVT filter....in fact many of us Vespisti remove the air filter and ride "bareback" for better cooling.
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Old 10-09-2013, 09:08 PM   #29
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It was a Yamaha oem belt, says Yamaha on it. The rubber strip on the edge of the front pulley was about 1/8" wide, and on both sides. It was right on the outer edge of the pulley. You can't run the engine without the cover in place, even stationary, because oil will come out through the holes that go to the sight glass which is in the cover itself, and requires the cover gasket to seal around where the oil goes through the crankcase and into the CVT cover. Could probably be plugged with something while running on the centerstand, but I wouldn't want to ride it that way.

As for the filter, yes it was oiled, with engine oil, as it says to do in both the owners and service manuals. I had squeezed out the excess oil. Around here an unoiled foam filter would be worthless. The air here is full of dust, and it would go right through an unoiled filter. The oiled foam filter on my dual sport bike will be caked with about 1/8" of oil soaked dirt from a one day ride in the desert. There will even be chunks of oily dirt on the bottom of the airbox, that had built up on the filter to the point where it fell off.


I find it odd that the front opening in the CVT cover has a filter, but the rear openings don't. I guess the idea is that the air will go in through the front opening with the filter, where the fan is, and come out the back. Dirt in the CVT is why I didn't like the idea of riding a scooter off road.


I think I will just replace the belt, gasket, 0-rings, and filter, put it all back together, and put it on Craigslist. I still have the Zuma 125, which is basically the same scooter with a different look. Not knowing what caused this makes me wary of trusting it again. I have ridden several hundred miles from home on this scooter. I was lucky to be only 35 miles away when this happened. My road service plan would not have covered towing from a few hundred miles away. Also, many of the areas I have ridden in have big gaps in cell phone coverage.
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Old 10-10-2013, 09:10 AM   #30
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Good idea, Jerry. Sell it, then get a SYM HD 200. Trouble-free and you'll still get 70 mpg.
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