Aftermarket Variator + Drive Belt = Failure at ~3,500 miles

Drivetrain upgrades, engine upgrades, or any other mods to gain speed or acceleration.

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Aftermarket Variator + Drive Belt = Failure at ~3,500 miles

Post by Hugh_Jaz »

Author of the 2015+ LED PCX 150 thread discussing the variator/roller weight/belt upgrade and its joy for freeway travel...

So, I was very happy with the Yuminashi v.2016 Variator and recommended aftermarket reinforced belt. This is until the belt snapped yesterday. Clutch engaged immediately but the belt jammed the variator so the motor shut off and wouldn't restart - I was able to coast to an exit and all was well - I have since re-installed the OEM parts and the machine is safe at home. From the looks of it the rollers might need replacing and obviously the belt but the variator seems fine - still rather than use the OEM belt on the Yuminashi Variator I went full stock.

Now - to be fair I think the manufacturer covered themselves by saying the belt should be checked/replaced about every 1,000 miles or so and I didn't... and overall the part worked like a dream so I can't say I regret the purchase (I did the work myself and it was barely over 100 USD all in), but to those who are wondering and thinking about the Yuminashi purchase - it works great but don't think you can get away with leaving it alone expecting it to work reliably under the Honda maintenance cycles. I would say based on my mileage I would be looking to crack it open about every 2K miles.

So - back to stock and frankly since it's a freeway commuter I need I may be trading it in for that Burgman 200 after all (even though the burg' looks less cool). I'll mull it over I may just buy another bike since I'm still smitten by the sexy PCX. The stock parts back in makes the machine quite a bit less revvy and rather more quiet and sedate an experience.

All in all I don't regret having done it, and I'm only a belt and possibly rollers away from doing it again, but I think I'm trying to bang a square peg in a round hole to ask the PCX to be a daily freeway commuter and given that is the case if I get another slightly bigger scooter I won't want two...
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by homie »

Thank you for the report, these things need to be followed up and you have done it. I'm glad you managed the failed belt so well, credit to your attitude. 3500 miles does not impress me much and this is noted for future members thinking to install the Yuminashi v.2016 Variator and recommended aftermarket reinforced belt. We will need to hear from others before going too negative since you liked the performance but endurance will factor and some will say.... no thank you.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by chicaboo »

Hey Mr Jaz,

Did the belt show signs of excessive wear on the outside edge where it may have been riding too high on the stock drive face?
I'm wondering if your higher speeds on the highway commute had the belt sitting past the edge of the drive face and unsupported.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Mel46 »

I have read of some other Yuminashi products that have failed too soon. That is one reason I decided not to go that route with my bikes. It is not that they make bad products, but many of them have not been tested for any length of time before sales to the public. Also, if you are using the PCX as a commuter bike ON FREEWAYS for any extended amount of time, you might be better served to get a larger displacement bike or put in a big bore kit. As the question above brings to light, if the belt is riding at the very outside edge unsupported for any length of time it could easily fail.
It is my understanding that the NCY variation and drive face combination solved this problem. Still, if anyone is going to run their bikes with these upgrade kits, it would be in their best interests to check the belt ever so often, just for safety's sake.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Hugh_Jaz »

Well I can't upload a photo now but there are significant areas of the belt which show almost no damage, it does not look threadbare or split on basically half the belt... Which is a little concerning actually. I will try and get some photos up later.

But honestly I do think the part served its purpose for me and maybe with just a little more tlc and checking would have lasted a fair amount of time.

And it really makes me mad Honda put that absurd gearing in they have basically ruined a great bike...
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Eiron »

After reading this post, I went back & reread Yuminashi's recommendations. Here's what they say on their "V.2016-2" variator kit page:
The rollers should be checked/changed every 1600km/1000 miles (per maintenance schedule) to keep your scooter running tops. Over time, roller weights will develop flat spots which will impair the performance of your scooter. One will have this sooner as others and this based on the performance from your engine and your personal drive style.

If you spend a lot of time on top speed then this will demand a lot more from both, your roller weights and your v-belt, so both will need to be replaced sooner in this case as if it would be the case for someone with a moderate drive style.
So, they don't actually specify a check interval for the belt, but rather the rollers. They also specifically mention "If you spend a lot of time on top speed ...", which is where you're obviously riding. You put 3,500 miles on your PCX in 4 months! I've put about 2,500 miles on mine in an entire year. Most of my riding averages around 45 mph on surface streets, & my commute is only 12 miles. I'm reasonably comfortable believing I fall into their definition of "a moderate drive style."

My main reason for this upgrade was for my infrequent runs to neighboring towns. The main arteries connecting these towns are typically marked at 65 mph, & most car drivers are going 70-75 mph. Being a vehicle with a 63 mph max speed made me uncomfortable, & forced me to look for back roads with lower speeds (& longer travel times). This upgrade provides me with enough comfort margin to take the main arteries & not worry about angering car drivers because of my slower speed.

I'll check my belt & rollers next Spring, when I should have about 2,000 miles on them. Gates has an excellent reputation, so I'm a little surprised that your drive belt snapped after only 3,500 miles. (Honda recommends OEM belt replacement at 15,000 miles!) Besides flex fatigue, I wonder how hot the belt gets when run continuously at WOT? I'm very interested in seeing your pictures when you can get them!
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by chicaboo »

Aftermarket variators cause the belt to ride higher on the pulleys, so if you don't upgrade the drive face and then do a lot of high speed riding, the belt sits out past the edge of the stock drive face and wears out more since it's not fully supported on the side. Aftermarket drive faces (NCY, etc) are typically 14° and 120mm diameter, whereas the stock drive face is 15° and ~117mm ish in diameter.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Hugh_Jaz »

OK - Pics!!!

Most interesting to me is that the belt seems to be in such good condition where it isn't actually snapped...

Marks on the variator could have happened post-snapping... but they're on there pretty good since I've already done a once over with some brake cleaner to look at the face without grime...

Not sure if there is much to learn here or not - happy to post more pics if anyone thinks it would help.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by homie »

Looking at this, I wouldn't think anything but defective belt so far.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Mel46 »

If you look at the edge of the belt you can see where it was rubbing against something. On the variator itself it looks like the belt stayed in the middle a lot, which is good, but then it also shows signs of the belt riding on the outside edge. I can't tell if the obvious marks on the outer edge are just from when the belt broke, but if you look closely it looks like there is some wear on the outer edge of the variator as though the belt has ridden there normally too. Aside from the broken belt, I don't see much out of normal except the possible marks on the outer edge of both the belt and the variator.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Eiron »

chicaboo, unlike the NCY "assembly", these Yuminashi kits come with both the variator & drive face halves of the drive pulley assembly (along with a new boss & 10g rollers). But I think you're absolutely right that having mismatched face angles would cause issues!

Hugh, do you know the diameter of the Yuminashi variator & drive face?
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by homie »

I see it now Mel, you might have it right. The Yuminashi kit squeezed the belt up over the edges of the faces and this caused separation stresses along the line shown in example 'A' like where it was about to happen in example 'B' and did happen where the belt broke.

Am I getting this right? You can't ride your belt over of the faces or you suffer premature failure at the gain of short term performance enhancement. About 3500 miles with Yuminashi :roll: good post
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by homie »

Nobody is going to want that... unless you are racing other PCX's :lol: :lol: :lol:
Put in another belt, maybe a cogged one or go to NCY kits.

http://www.ebay.com/itm/Honda-NEW-PCX-1 ... 1728724392

http://www.hondapcx.org/viewtopic.php?f ... ogged+belt
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by chicaboo »

Eiron wrote:chicaboo, unlike the NCY "assembly", these Yuminashi kits come with both the variator & drive face halves of the drive pulley assembly (along with a new boss & 10g rollers). But I think you're absolutely right that having mismatched face angles would cause issues!

Hugh, do you know the diameter of the Yuminashi variator & drive face?
Ahhh, so the Yuminashi must just squeeze the hell out of the belt up past edges of the variator and drive face. They do claim the highest speed, so that's one way too do it. Looking at the pictures there's a wear line in 2~3mm from the edge of the belt, probably where it was proud of the pulleys.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Hugh_Jaz »

Well there was only one way this was going to end... So see you guys on the Forza forum.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by YUMINASHI »

Gregory Stuart asked me to take a look to this conversation, so thank you for the head's up Stuart, and after doing so it makes me think that the heat of the engine make the belt snap.

We have spend a lot of time and effort to find the right balance between allowing the belt to rise and higher RPM's to gain top speed.
Most companies let the belt rise until the belt is stretched so much so that it finally will snap, our variator have literally build a block in to avoid this, so that the belt can't rise anymore at a certain point, and the RPM's need to take it over then to gain more top speed.

You can see very clear on the displayed pictures here that the 2 variator halves are touching each other, hence slightly damage on the fixed drive, near the center of the variator.
So when the two variator halves are touching each other, the rise of the belt is blocked at that moment and it can't rise any further.

That's the moment where the RPM's need to take over to make more top speed.

We did several tests before, and we had one certain moment with a engine configuration where we where able to make a brand new original Gates Powerlink belt snap in less then 20Km time with a engine producing a lot of heat.
We improved the ventilation on the cover with machining a part out of the cover at the very end from the cover (right hand side once installed) to have a gap for the ventilation, and we didn't snap the belts anymore on that very same bike without changing anything on our variator.

Before we did that, we snapped at least about 5 belts on that bike.

So we changed nothing on our variator, only improved the ventilation/cooling capacity for the belt.
Our variators make a perfect fit with the angle from the v-belt, so we don't use 14 degrees or 13.5 degrees flanks because we know that this would eat v-belts and will make snap your belt very soon.

Talking about our variators which would allow the belt to rise to high is a non fact and out of order, this isn't happening, we block the belt..
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by homie »

Any one have a picture of this block that keeps the belt or these ventilation covers he's talking about? I don't think the poster had either on his bike so yea we probably will be talking about not using these if people don't have modified covers and belt keepers LOL.
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Hugh_Jaz »

Thanks for the feedback I'm continuing to keep an eye on my post.

A couple additional details just in general and of the day:

In general (all speeds indicated not GPS):
- rode 17 miles each way of which 30 altogether were freeway most days it wasn't raining, which in CA is often
- Saw 70mph almost every day in parts
- "cruised" between 60-65 on flat ground assuming no traffic
- traffic was fairly frequent - especially going home (California San Francisco Bay Area) - not an aggressive lane splitter
- Bike was 2016 absolutely stock except for GIVI screen and B47 topcase (plus obviously the variator)
- installed myself using torque wrench and stupid variator tool that falls off... ugh...

Some outright performance stats I stand by:
- never saw higher than 78
- never hit the rev limiter after I installed the Yuminashi part
- in stock form, before the part I felt like maybe I got lucky with a strong motor or did a good break-in because hitting the rev limiter was something I constantly had to watch for and it was very annoying - which of course was 63-64 mph (WHY?!?!?)

On the day:
- ambient temp probably low 70s Fahrenheit (not hot I might point out)
- going up slight grade, no traffic, approximately 60mph into a headwind (close to WOT)
- just finished a flat section also with no traffic into headwind but stayed in slow line and was probably mostly under 60... I do have some mechanical sympathy

Anyway - happy to keep answering questions but just to satisfy curiosity I think more than likely I got a bad belt and nothing more, as homie first opined right after I posted pics. Don't think anybody really has anything to answer for :)

Ride safe all!
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Hugh_Jaz »

I should probably just add that although there may be obvious reasons for me thinking this is true, the combination of rollers, engine response and top speed with the Yuminashi pieces was such a vast improvement over stock that I could only tolerate that PCX back in stock form again for about a week before I traded up to the Honda Forza, which I think given my needs was a wiser purchase I arguably should have made to begin with.

I am an unashamed Honda motorcycle fan, but their decision to so thoroughly ruin a scooter with this design choice, and the lack of awareness on the part of dealers and even the internet at large (I read up on the PCX extensively before buying it and sadly my purchase predates the "Highway Hoppers Scootout" review which reliably reports the problem) is a real travesty.

I recommend the PCX whenever I can to anyone who asks about it but I never forget to add that it will not reach the freeway speed limit even though it has more than enough power to do so.

Still - loving my Forza... but about that windscreen, or the lack thereof...
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Re: Aftermarket Variator + Drive Belt = Failure at ~3,500 mi

Post by Eiron »

homie wrote:Any one have a picture of this block that keeps the belt or these ventilation covers he's talking about? I don't think the poster had either on his bike so yea we probably will be talking about not using these if people don't have modified covers and belt keepers LOL.
The way I read the response from Yuminashi, the combination of their variator & drive face is designed in such a way that they "bottom out" ("block") against one another before the belt can climb too high on the pulley faces. Similarly, I read the ventilation comment as "we made some holes in the trailing edge of the cover to improve airflow." I will admit that I'm thinking of adding some ventilation to the cover after reading this. I suspect that the toothed backside of Honda's belt improves both flexibility of the belt & airflow around the belt, both of which would allow the belt to remain significantly cooler.
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