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Does lighter clutch weights hurt top speed?

14K views 32 replies 9 participants last post by  Hunterworks 
#1 ·
Not sure if I lost top speed or not.
With 22 gram weights, I got 57.3 MPH at 1000' elevation while hitting the rev limiter.
Now with 16 gram weights I can only get 54 MPH but I'm now at 6,500' elevation and I'm not hitting my limiter.
 
#2 · (Edited)
It is mostly elevation, I am editing my original comment, didn't catch you had a X2

16 might affect top speed in this vehicle, I would be running maybe 18 or 20 for elevation and stock tires

However since we have not released anything for a X2/X4 yet, I can't say for sure the above is what I would. I really hate to get the cart ahead of the horse
 
#3 ·
Lighter weights may not affect your top speed if you haven't bypassed your speed limiter but it will limit your top speed if you have bypassed your speed limiter. 16 grams should make you hit your rev limiter very easily, not the other way around over stock 22 gram weights. I'm using 22 gram weights and am hitting 63-64 MPH with 27" Terrabites, HMF exhaust, Weller ECU flash, and Hunterworks machined sheave. I can tell you if I had 16 gram weights in there I would not be hitting those speeds. I'm at about 5500'
 
#4 ·
A lot of variables determine top speed, tire size, reflash, elivation, gears, etc. think of clutching as a ten speed bike. Lighter weight is that low gear easy to pedal but gets to top fast. Lighter weight is is high gear hard to pedal and takes longer to get there. An example where a change in weight will show changes in speed would be like going from a 14gm to 22gm. A large swing in weight. Way smarter people here when it comes to clutching so correct me if I’m wrong.
 
#5 ·
While the basics of the Yamaha CVT haven't changed over the generations, the tuning and engines behind it have changed dramatically. The old 686\708 cc singles were more HP vs torque oriented engines. The new 847 cc engine is an absolute stump puller in comparison and likes lower revs in comparison. The X2/X4's secondary spring looks like you could pull it off and stick it on the front suspension of a 3500 series truck. That spring pressure is fighting your primary weights. This is why you can't use Gen 1 weight tuning and apply it to X2/X4, which is also a much heavier vehicle.

I think it's ludicrous that Yamaha big tire kit from Gen 1 is nearly the same as the X2/X4. It's like someone got lazy and said 'let's just reuse it'. It's like taking a heavy tractor or a turbo diesel truck and saying: 'we need more torque from this thing, let's put more-ridiculous gearing than what it already has'

https://www.wolverineforums.com/for...clutch/21066-wolverine-x2-x4-clutch-mods.html
 
#7 · (Edited)
Yes, all things being equal. But the challenge is that all things are not equal. Clarify what is max RPM, for instance, is that the max the engine will turn under its constraints or the max a limiter allows? And remember to not just think of the primary as being all the way 'open' cause of centrifugal forces on the weights, but it works in conjunction with the secondary to situate the belt to the MAX position. The secondary spring is resisting that happening and the size tires are the gearing effect that is also resisting the process and the horsepower/torque available to get the power through the drive train to the ground. So these variables is why this is called CVT 'tuning'. If you do not have enough horsepower/torque at different gearing effect then you may not get the same results. That is said without consideration for imposed limiters, just theoretically. Tuners spend a lot of trail and error or dyno time trying to get a recommended package, but each vehicle is different with weight carried and tire sizes, etc. Hope this helps.
 
#12 ·
Your right about the speed limiter, that's what I was hitting for sure. (speedo said 52)

I wish someone could simply answer my question.
Do lighter weights hurt your top end MPH?

I may be getting an aftermarket sheave but currently my only option is JBS.
 
#16 ·
I'm fairly confident that it's not the elevation that's killing your top speed. Sure elevation robs some HP, but you all are ignoring that I'm at 5500' and the 2019 X2 I tested the Weller flash on (on an otherwise stock vehicle) hit 56-57 MPH, which other test vehicles at sea level haven't done any better.

The loss in HP is about 3% per 1000'. In reality I think it's much less because we're not driving pencils. If you have a windshield and/or roof we're trying to push a billboard sign flat against the wind at 50-65 MPH. Now, at higher elevations, that same thin air which reduces our HP also reduces our drag.

So my X4 should be making ~75 HP with my HMF exhaust and Weller Flash. 75 x (1-(5X.03)) = 63 HP. Based on this I shouldn't be able to even match a stock X2/X4 with NO mods. Tell me how I'm hitting 63-64 MPH?

Bottom line: I don't think it's the elevation killing your top speed. I could be wrong, but I'm willing to bet on my theory that I'm right and it's your new weights. If you just have to scratch that itch, throw your stock weights back in at the same elevation and you have your answer.

Ask me why I'm asking Todd/Michael to make heavier-than-22 gram weights?

You want it stated plainly?

I believe lighter roller weights will probably increase your ability to reach a specific top speed but will probably reduce your maximum top speed on an X2/X4 with a machined sheave simply due to the humongous secondary spring those weights are trying to fight against


The above statement applies to flat ground running and not trying to do top speed runs down Mt. Everest.

I wish your question could be simply answered but it can't. Happy now?
 
#28 ·
I'm fairly confident that it's not the elevation that's killing your top speed. Sure elevation robs some HP, but you all are ignoring that I'm at 5500' and the 2019 X2 I tested the Weller flash on (on an otherwise stock vehicle) hit 56-57 MPH, which other test vehicles at sea level haven't done any better.

The loss in HP is about 3% per 1000'. In reality I think it's much less because we're not driving pencils. If you have a windshield and/or roof we're trying to push a billboard sign flat against the wind at 50-65 MPH. Now, at higher elevations, that same thin air which reduces our HP also reduces our drag.

So my X4 should be making ~75 HP with my HMF exhaust and Weller Flash. 75 x (1-(5X.03)) = 63 HP. Based on this I shouldn't be able to even match a stock X2/X4 with NO mods. Tell me how I'm hitting 63-64 MPH?

Bottom line: I don't think it's the elevation killing your top speed. I could be wrong, but I'm willing to bet on my theory that I'm right and it's your new weights. If you just have to scratch that itch, throw your stock weights back in at the same elevation and you have your answer.

Ask me why I'm asking Todd/Michael to make heavier-than-22 gram weights?

You want it stated plainly?

I believe lighter roller weights will probably increase your ability to reach a specific top speed but will probably reduce your maximum top speed on an X2/X4 with a machined sheave simply due to the humongous secondary spring those weights are trying to fight against


The above statement applies to flat ground running and not trying to do top speed runs down Mt. Everest.

I wish your question could be simply answered but it can't. Happy now?
Well actually I retested at 7000’ elevation.
Just a bit longer of a straight a way.
I bet at my normal elevation of 1000 I will hit it much fast.
Thanks for retesting and confirming. You're out of the sweet spot for the X2/X4's engine torque range with the 16 gram weights for high speed running.
 
#17 ·
The X4 makes 11 more HP than the Teryx. It will also beat it in a drag race. Everyone I know that's gone from a Teryx to X2/X4 says the X4's power is vastly superior



So why does this review say this?

"WHICH IS THE FASTER TWIN?

Both have rev limiters that kick in at 50 mph in high, so both top out at 50–51 mph (maybe 52 on a downhill). We got 31 mph out of the Teryx4 and 29 mph out of the X4 in low at about 2800 feet of elevation. The 783cc Teryx V-twin is tuned for torque, and the throttle map is a little more aggressive, making the shorter-stroke Teryx4 more peppy and fun on the trail. Yamaha’s new 847cc inline twin has a comparatively longer stroke (80.2mm versus 69mm) and is also tuned for bottom-end to midrange power and torque, but Yamaha also designed the Wolverine X4 with a very large-volume intake tract for quiet running. With that and the tuning for the YCC-T fly-by-wire throttle mapping, the larger-displacement Yamaha accelerates slower than the Kawasaki. One test driver said, “It’s like the Teryx has a quarter-turn [dirt bike] throttle and the Wolverine has a half-turn throttle.” The tie-breaker goes to Kawasaki, although the X4 high-altitude CVT kit with the OEM 26-inch Bighorns does improve acceleration for more sport-minded drivers."

https://utvactionmag.com/shootout-kawasaki-teryx4-le-vs-yamaha-wolverine-x4-se/

It's because of this:

"We followed up with a long-term test of the Special Edition in July 2018 and modified the X4 CVT in September for 27-inch tires"

"So, the X4 SE starts out at $250 more than the T4 LE, and the 16-gram CVT clutch kit adds another $50. Yamaha’s accessory VDF-14SXS-01-07 27-inch tire and 14-inch wheel kit adds $1230 for a total of $1480 more than the Teryx4 LE (as tested)."
 
#19 · (Edited)
Any changes made in the CVT are like robbing Peter to pay Paul. When you gain something you lose something. We have to look at it as compromise. Except in the machining of the sheave where top and bottom gains can both happen.

I can totally see lighter weights affecting its top speed when the rev limiter is at play!
I’m no CVT expert and maybe this is not correct but it’s how I’m thinking it in my little brain. The machine accelerates as the CVT cycles up to its highest ratio, after that any increase in speed happens by way of Engine rpms. With heavier weights the CVT has hit its highest ratio at a lower engine rpm. Now there is more speed to be gained by way of rpms before hitting the limiter???

That said, elevation really affects performance for sure but i think massive is right about this and he’s got a great deal of experience playing with sheaves at this point!
 
#20 ·
As mentioned in the first reply on this thread most likely the issue for this is elevation

Now on weights, there comes a point that the weights are too light that they can't overcome the spring pressure in the secondary and then the clutch can't close all the way, but assuming the clutch closes then the weight of the weights has not affect on top speed as a general rule. I guess if you went the other way and put too heavy in then it would shift out too quick and be hard to overcome the low rpm kinda like a 5 speed shifted into 5th too quick

But if you are in the range of weights that will close the clutch then in this case the elevation is what is most likely causing this.

I personally have not put 16gr in a X2 or X4 yet, lightest for me is 18 so I can't say 100% that that 16 is not affecting it. But simply based on the info given I would suspect the elevation.

You won't know until you swap the weights around

Todd
 
#21 ·
I didn’t read the the original post through enough. I just now noticed that it’s said “not hitting the limiter now” sure does make one think it has to be elevation or not fully overcoming the secondary spring. Wouldn’t it be nice to have your own dyno and just watch what’s going on in there with cover off! Is it possible to just retest at the same elevation as before to try and rule it out?
 
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#23 ·
That would be something for sure!
 
#24 ·
DWRAT,

A big thing working against you right now is too many factors to narrow down the one root cause of a speed loss. There are many factors that come to play in the speed game that we are all chasing (whether it be for actual speed or as a measurable check of performance). Going from 1000' to 6500' can cause its own issues as can going from 22gr to 16gr weights. Things get even more complicated when I can't tell if you are running a machined sheave (JBS is the only one with a consumer offering at the moment), OEM weights vs HV or OD, Greased or Greaseless, etc.

So, to answer if the weights themselves can affect top-speed, the answer is YES. There are many things that work together within just the CVT that can gain power (torque) or speed. When you consider that there are 8 weights within the Sheave, making a change in weight will be multiplied. So in your case going from 22gr to 16gr is a 48gr change. With spinning mass, this will allow you to spin up faster, but will not have the same force to overcome the spring allowing the "shifting". In other words, you will be able to rev faster, which will build your power faster, but it will not have the same force to push the secondary at the same rate.

Elevation can also effect the overall performance of the engine. And like Massive said, the "thinner" air also presents less drag. This side is much more complex than I am confident in my understanding of, yet alone my ability to explain.

Furthermore, if you are running grease in your sheave with your weights, that will also add a factor to the situation. The quantity of grease is really difficult to measure and perfect.
 
#26 ·
So are you saying elevation was a factor? You retested at lower elevation?
 
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