beware of broken belts

Discussion in 'Battle Scooters' started by JerryH, Oct 4, 2013.

  1. JerryH

    JerryH Banned

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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.
    #21
  2. tortoise2

    tortoise2 Been here awhile

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    Very plausible since the variator is pretty much a heat sink for the crankshaft, and "insulated" by TWO covers on the Vino 125.

    <EMBED type=application/x-shockwave-flash height=315 width=560 src=//www.youtube.com/v/L4Uh4-i7DOk?hl=en_US&version=3&rel=0 allowfullscreen="true" allowscriptaccess="always"></EMBED>

    <EMBED type=application/x-shockwave-flash height=315 width=420 src=//www.youtube.com/v/seXiFIlbeYg?hl=en_US&version=3&rel=0 allowfullscreen="true" allowscriptaccess="always"></EMBED>
    #22
  3. ohiotj

    ohiotj Adventurer

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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...
    #23
  4. Moat

    Moat Been here awhile

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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.
    #24
  5. k-moe

    k-moe Long timer

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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).
    #25
  6. gogogordy

    gogogordy Long timer

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    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.
    #26
  7. gogogordy

    gogogordy Long timer

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    No, don't oil CVT filter....in fact many of us Vespisti remove the air filter and ride "bareback" for better cooling.
    #27
  8. JerryH

    JerryH Banned

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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.
    #28
  9. blugg1

    blugg1 Been here awhile

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    Good idea, Jerry. Sell it, then get a SYM HD 200. Trouble-free and you'll still get 70 mpg.
    #29
  10. blugg1

    blugg1 Been here awhile

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    Actually, you can buy mine if you want to. We both live in AZ so it shouldn't be too difficult.
    Just changed the fluids and installed new Shinko tires. Shoot me a PM if you are interested.
    #30
  11. k-moe

    k-moe Long timer

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    ...and a better engine IMHO.
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  12. steve_k

    steve_k Long timer

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    Are you sure the belt was even changed the first 2 times?
    #32
  13. JerryH

    JerryH Banned

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    Yep. I'm the one who changed them. Right around 10,000 miles. Did not see anything out of the ordinary when I replaced them. Both were oem Yamaha, just like the one that shredded.
    #33
  14. steve_k

    steve_k Long timer

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    Ah, good... You did the work so you would know for sure! Have seen few threads on the net about timing belts that were paid for but never changed and motors wiped out shortly after.

    It's a bummer to have yours go out so soon.
    #34
  15. JerryH

    JerryH Banned

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    The problem is I never found out WHY it broke so soon, and am afraid the new belt could break at any time, leaving me stranded again. Plus I have a fairly new Zuma 125 with the same belt and drive system, and it has around 4,000 miles on it. Don't know how much I trust it either. I was planning on putting some miles on it this winter, including a couple of 1000+ mile trips. Now I'm not so sure.
    #35
  16. blugg1

    blugg1 Been here awhile

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    Maybe you should sell both the Vino and Zuma and get a scooter with a larger engine, say 200-250cc's. Especially if you're planning 1000 mile trips. You'll have a much better time on a Kymco or a SYM or whatever on longer trips.
    #36
  17. Moat

    Moat Been here awhile

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    I'd just bring along a spare belt and the required tools to change one out on the side of the road, if needed - and not worry about it. If one were to compare the time spent over a 1000+ mi trip doing chain maintenance vs. changing a belt... probably pretty close. The price of adventure! :1drink
    #37
  18. gogogordy

    gogogordy Long timer

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    An anomaly I'm sure.

    Nothing to get your panties bunched-up over. Don't let it ruin your fun. Coulda been a new tire blowing out...that happens too.
    #38
  19. Dan V.

    Dan V. Been here awhile

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    Just something that is gonna happen. When we went on out trip to dragon land each scoot had a spare belt even though we could not change it out on the roadside. Wanted to have one aboard so as not to blow the trip waiting on a local mechanic to source a belt if one was needed.

    Over the past years, accumulating thousands of collective miles, our club rides have never had a belt failure from normal circumstances. This is with scoots of all different sizes, and with varying states of maintenance and equipment age.

    The only belt mishap was from a guy who kept mis-installing his variator, where by the nut was tightened on the shoulder of the crank and not on the variator face itself. This would cause the variator to work loose while riding, eventually ruining the variator, belt, and the crank itself.

    That video above with the FU variator had to be caused by a bad install. Obviously something came loose, and friction heated things up to melt the sliders. I can't even imagine how it would run, but someone obviously ran it quite a while like that. I can hear it now "It was making a funny noise while I was riding it"!

    Jerry, you got a bad break, or bad belt. Maybe AZ heat has something to do with it. Still no reason to dump the Vino.
    #39
  20. Chillis

    Chillis Land Barge Pilot

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    Jerry, when your belt broke, were you going down hill traveling faster than your normal top speed?

    I say this because on my Aprilia, I can go down a large hill and hit almost 70mph indicated with the Malossi variator due to its ramp design. In pushing the belt out that far it wears on the engine case and that was the last time I went for a top speed run.

    If you have pushed the envelope with your bike you could have damaged it prior to its failure.
    #40