Low mileage belt breakage (2K miles) and roller orientation

[SaltyDog]

Hello folks, I just started riding the Downtown again, but the belt broke with less than 2K miles on it.  It was an OEM belt, purchased direct from a Kymco dealer while visiting Taiwan (part # 23100-LEA7-E01, which is the same as listed for the US models) and installed in early 2018.

I've still not been able to identify the root cause for it to fail.  Pulleys all feel smooth, and with a new belt installed, the variator and clutch assembly all appear to work fine again.   But I wasn't 100% sure I got the roller installation correct.  Are they supposed to be installed with the side having more plastic on the side as shown in red?   
The service manual says they are supposed to be installed with the more plastic side toward clockwise, but after thinking how the engine rotates not sure if they meant that is supposed to be "toward clockwise" while disassembled, or when looking at it post-assembly.
 

[CROSSBOLT]

I may have missed it but I think the rollers are cylindrical. More plastic? I think they are the same diameter from one end to the other....

[Iahawk]

was watching a video from Robot with Vespa Motorsport the other day and he was working on the variator from his BV 350. He mentioned that the rollers were supposed to be installed with something oriented to the clockwise position...and he specifically said that clockwise meant as you were looking at the open variator, and not as installed on the scoot.

Now this doesn't definitively mean this applies to your scoot but I'm realizing that all these variators seem to work the same way, no matter the manufacturer.

[Stig / Major Tom]

The side with the most plastic goes like this....


These were lifted straight out of a factory install....and set down & not flipped over.

Stig

[CROSSBOLT]

The side with the most plastic goes like this....


These were lifted straight out of a factory install....and set down & not flipped over.

Stig

What plastic?!

[scooterfan]

The side with the most plastic goes like this....


These were lifted straight out of a factory install....and set down & not flipped over.

Stig

These rollers look like aluminium ?
If so - do they last longer / shorter than “ceramic “ (or whatever it is) type rollers ?

[Stig / Major Tom]

Plastic, polymer, nylon, ...whatever, .but never heard of metal.
Lots of these are dark.
One end is often more open than the other. The end with the most plastic rides against and slides along the carrier wall when in motion..
Hard to imagine a roller causing a belt to break unless it really came untracked in the carrier!
I'd check for smooth operation of the clutch as well.
If another Kymco belt breaks again....then you've got an issue in there.
Stig

[SaltyDog]

Thanks everyone - the direction given in from Stig's post and Robot's video make more sense considering the engine's rotation.  I even dug up an older service manual for a Kymco Xciting which was consistent with Stig's image, so I think I've got them installed correctly now.

As to root cause for the failed belt, I don't think it was rollers falling out of their track.  Everything seemed to be in place when I removed that assembly.  Well, that is until I popped open the ramp perhaps a bit too abruptly and rollers went everywhere...   Also, the width of the still-intact portions of the belt that remained was only ~21mm, so whatever caused it appears to have happened over time.

Anyway, I did re-check clutch operation today in the garage and on a test ride - it still operates smoothly.   The only other potential issues I could think of are:
1) Belt age.  I still have the original packaging from that belt, and although it was installed on the scooter in 2018, the belt itself was manufacturered in 2013.
2) Riding style.   Most of the miles on this belt were long-distance miles as opposed to just cruising around town or maybe the occasional 20~30 mile trip.   One long trip was around 900+ miles stretched across 3 days.  Another was the around 200+ miles.  Of those 2 long trips, I pretty much cruised at a speed of 70mph or so.

[scooterfan]

Quite interesting. A couple of days ago Cbr125 reported a belt break on his much smaller Agility. To my understanding he also often travel at high speed on his scooter.
This is a much heavier scooter, and the belt broke after long trips at similar speed.

This makes me wonder whether high heat and the speed the Variators were rotating at high speed could cause belt breaks like this ? Maybe excessive heat caused both belt failures ?

Were these long strips solo rides or did you carry a passenger ?

[Stig / Major Tom]

Would think belt age (and perhaps conditions where stored for those years?) would be much more likely the cause of your belt's failure.
There are a great many scooters riding at full song all over the world, generating a lot of the expected (by the manufacturers) heat in the CVT. Belts are not exploding in high temperature environs....most scoots being used in hot climates.

Maybe you just got a bad one....
Like I said, I'd try a new OEM belt and then give it a look (measure) after 1,000 miles of your normal riding.

Do keep us informed …..we're all learning stuff here.

Stig

[john grinsel]

With over 400,000 miles of rubber band drive scooter experience, I would go with "belt age".