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I realize that no matter what the spring's function is in the clutch, higher spring rates will require higher RPM for them to actually perform that function. My question was regarding the specific statement "...and also when the scoot starts to move."

I know this may seem overly pedantic and perhaps a little argumentative, but I'm really just trying to make sure I'm grokking this correctly.

It seems to me that if you put the strongest contra spring (the red one IIRC) in the clutch, but retained the stock clutch-arm springs...then the scoot would still not 'start to move' at a higher RPM, since the clutch arms would engage the bell (and pass power through to the wheel) at the same RPM as before.

The difference of having the stronger contra spring would lie in how long the front/rear pulley ratio would remain in 'low' gear, with the contra spring resisting the variator's attempt to close and pull the belt deeper into the rear pulley (by forcing it open), and how quickly it 'downshifts' as RPM drops.

I'll confess to still being on a learning curve as to the functioning of the typical CVT found on scooters, but.... this doesn't quite mesh with my understanding.

To start, I'm presuming that the Contra-spring in question is the single large coil spring that presses the two halves of the REAR pulley together. (If this is wrong then the rest of this post can pretty much be ignored)

I've seen the function of this spring explained as causing the rear pulley to remain in the 'closed' position longer, preventing the belt from forcing it 'open' (in direct opposition to the efforts of the three weights in the variator to do just that), resulting not only in an extended time in a 'lower gear', but also improving 'downshift' when coming 'off throttle'.

As I understand it, the point at which your scoot begins to move will be when power is applied to the drive wheel via the clutch-bell as the three clutch arms swing out to engage it. These three clutch arms are 'held back' by three smaller double-hooked coil-springs until sufficient RPM-induced centrifugal force causes them to swing out and engage said clutch bell.

As I stated before, I'm still learning how these things work, so if I'm 'off' in my understanding...be gentle!

Something I had to 'train' my brain to accept with filters, is that it's the total surface area of the filter that you need to be concerned about, not the physical dimensions as installed. An 'accordioned' filter element like that may look small, but the overall surface area is actually huge.

Using your supplied photo (and making some ballpark presumptions on size since I have nothing to compare it to) we can do a little math:

PRESUME that:
Both 'ends' of the filter element are finished in the 'down' position
Each fold is roughly 1 inch tall
The length of the filter is 8 inches
and
The width of the filter is 2"

As installed, the filter opening is approximately 16" square (8"L x 2"W), or .1 (repeating) square feet, or a shade over 1/10 of a square foot.

HOWEVER...by the photo there are 33 folds (^^^^^) facing up. If each fold = 2 vertical surfaces (one up, one down = ^), then we can extrapolate 66 'surfaces' at roughly 1"x2" area (or 2 square inches) for a total of 132 square inches, or .916(repeating) square feet, or a shade over 9/10 of a square foot.

If you could fit a flat square of identical filter paper over an airbox opening of that size, would your opinion of 'restrictiveness' change?

With regard to needing to press (or pound) the gear onto the shaft: I see many admonitions not to try and heat the gear with a torch, but I haven't seen anyone try the old 'oven and freezer' method.

Many moons ago I had a power steering pump go out on my RoadRunner. I bought a new one, but being the inexperienced lad that I was, I did not know they did not come with the pulley attached. The pulley is a 'press-fit'. Cost me $20 to have a shop press the old pulley off just to turn in the core (the new pump was just a shade over $30 so that charge seemed rapacious).

To reinstall the pulley on the new pump, I simply put the pulley in the oven at about 250 degrees, and put the pump in the freezer. After about an hour (to make sure they had both achieved limits of their respective temperatures) I took the pump out of the freezer and (using a welding gauntlet) pulled the pulley out of the oven and just slipped it right on.

In fact.. it slipped on so easily I initially thought I had the wrong pump! It seemed like the shaft was too small diameter, but after a few minutes in close proximity to each other, the shaft warmed, and the pulley cooled, and when it was all said and done the pulley was bound up TIGHT on the shaft.

It seems as though one could do the same here: Place the gear in the oven, and the shaft in the freezer. I can't imagine that a mere 250 degrees (typically the lowest setting for a residential oven) would affect any tempering/hardening of the gear teeth (generally the reason given for NOT using a torch).

Irwin Bolt Grip (or similar knock-offs) work a champ on rounded nuts/bolts.




There are similar versions with straight 'teeth' that you hammer onto the bolt, but I prefer the kind that *don't* leave the tool attached if you can't break the nut free.

Something I've noticed about my 'new' scoot is that while up on the stand and idling, the rear wheel is in constant motion. Not too terribly fast...maybe about 5MPH equivalent...but it's a smooth steady turn, not a slight, pulsing twitch like I see in many YouTube videos.

When down on it's wheels and at a stop, there is a noticeable load on the engine (idle drops from a smooth 1400, down to a ragged and strained 11-1200rpm) which results in a 'pulsing' sensation in time with the idle. This pulse is so pronounced that it 'shakes' the bike making it hard to tell if it's the low rpm rotating mass of the engine internals shaking things up, or if it's a slight pull from the drive wheel (or both).

Now to my mind (and limited understanding of the CVT mechanics), a moving wheel at idle means there is *some* belt engagement occurring, which translates into unnecessary belt wear at stop lights/signs. This means that, while I *could* turn up the idle to stay steady at 1400rpm while 'on the ground', this would not solve the problem of the belt being at least partially engaged.

In fact it could exacerbate the issue, as the only reason I can think of for the belt to be moving the rear wheel is for the three clutch pads to be ever-so-slightly engaged, and a higher RPM would cause them to engage even more, resulting in 'automatic creep' (that phenomenon where an AT car will move forward unless you keep the brakes engaged). So either the belt or the clutch (or both) is slightly engaged and slipping at idle, which to me translates into unnecessary wear. If not for the noticeable 'load' on the engine at stop signs, I'd attribute the wheel spin on the stand to sympathetic drag.

The glaringly obvious solution is to replace the three small clutch springs with slightly higher rate springs to ensure that they do not engage at too low of an RPM. This should (in theory) eliminate the spinning wheel while on the stand, as well as the added load on the engine while stopped on-the-road.

What I haven't been able to determine through research is just exactly what effect swapping *only* those three springs would have on the rest of the CVT. I'm all about economy...I'm not terribly interested in neck-snapping acceleration, or tear-inducing top speeds so a complete weight/pulley/contra/clutch-spring revamp isn't in the cards (though I understand that a taller variator may result in better upper end efficiencies).

I can't imagine that simply ensuring the clutch doesn't engage at idle speeds would have any effect on the ret of the CVT's normal function, but I figured I'd lay my situation out for more experienced folks to chime in on...so, chime away! ;D


*Something else that just occurred to me (literally...just now, so I haven't researched it yet) is what exactly the RPM 'ratings' on aftermarket springs means. For example, the 1500rpm clutch springs...does that mean they begin to engage at 1500rpm, or that at 1500rpm they reach full engagement?