variator spacer mods ?

[ZOOMER46]

tis just occured to me,
that little has been said about experimenting
with the variator spacer length?

some occassional comments of that if you shave some of the length off the spacer you will gain some top speed?
BUT, how much do you shave?

or what if ,the spacer was even lengthened ? !

what are the benefits if any,thru the whole range
with a shorter spacer?

can the rear pulley be modified in any way?
other than the spring ?

are heavy front rollers and light spring at the rear best for cruising speed on the flat,along with the an
aftermarket variator and shorter spacer?

i have just fitted a polini variator to my zoomer with the 6x yellow rollers and the pullaway is not quite as good as the standard
one. this can't be rite?

[Dandy Dan]

When you shorten the spacer in essence you move the whole range of gearing up. It's like removing first gear from your cars 5 spd transmission and replacing it with a 6th gear.

The result of shortening the spacer is always worse acceleration off the line but it can yield more top end if you have the power to pull a taller top gear ratio.

From my experience, with the stock variator you gain about 1mph for every 1mm you shave off the spacer up to about 3-4mph. With an aftermarket variety there really is no reason to shave the spacer because the variator has a wider range of gearing so it can already push the belt all the way up. If you look at your stock variator you'll see a wear line that shows that the stock belt never rides higher than about 80% but an aftermarket variator should be getting pretty much 100% of the way up so a shorter spacer will just cause it to ride too high and hit the inside of the case.

If you lengthed the spacer in theory you'd be geared lower across the range which would be a good thing except our variators already start with the belt all the way down so it's not possible to be geared any lower. As a result, you'd probably be similar off the line but your top end would be worse.

In terms of gearing, the rear pully can not be modified other than the compression spring and clutch engagement spring which affect the shifting but not the absolute gear ratios. I guess you could try and machine the clutch shaft thinner which would gear you taller on the top end ultimately but that is a pretty risky idea.

For cruising along flat roads, you just want to ensure that you at your max gear ratio so a heavy or soft rear clutch compression spring doesn't matter as long as your roller weights are heavy enough to compress it all the way so you get to your max gear ratio. That's why you can use about 5.5g weights with the stock spring but you need to go up to 6.0 or 6.5g with aftermarket springs.

BTW, how's your Polini working out for you? What's your top speed now? Because you have the Metro gears you could probably go with lighter rollers (5.0g?) to get better pull away. Also, if you use the same roller weights but a slightly stiffer compression spring (yellow?) you'll get better acceleration off the line. If you use too stiff of a compression spring you will need to go with a bit heavier roller weight (maybe mix in the 3, 7.2 g Polini weights) to combact the stiffer sping.

Aren't you geared taller enough already with the Polini plus Metro gears? I imagine your top end must be plenty tall and all you really need now is better pull off the line which can be done with either slightly lighter rollers or a bit heavier compression spring.

[chanito]

Hey DD, i have a stock variator and go 45 mph
There is post on the how-to section about shortening the stock spacer and mod the outer face of the variator, is way cheaper than an aftermarket unit and work pretty good

[Dandy Dan]

chanito said:

Hey DD, i have a stock variator and go 45 mph

Yeah but you have a CDI too to rev past 8K

I'm not sure how tall I was geared when I had my modified stock variator because I had a CDI too so I didn't know when I hit 8K but it did feel quite a bit taller too. Actually shaving 1mm off the spacer wasn't that profound of a difference but when I shaved another 2mm or so off the inner lip of the outer plate that made the difference much more noticable. However, I found that I had quite a bit more lag off the line which is why I like my aftermarket variator.

Anyways, I have an extra shortened spacer (1mm shorter) and a shaved outer plate that someone can have for cheap if they want.

[jumpjunky]

Actually, Dan, I need to respectfully diagree with you.

These tranmissions are CVT's (Continuously variable transmissions). On the engagement side, by shaving the spacer, we're in essence narrowing the distance the primary needs to close to squeeze the belt. Once this engages, both clutches do their thing and shift out all the way. The secondary tranmissions here are 'torque sensing'. This is 'continously' shifting through an infinite gear ratio. Shaving the spacer does nothing to this shift. The CVT's compensate. One could argue SLIGHTLY different engagement characterisitcs, but that's a whole other topic.

Where we see the benefit of shaving the spacer is at the top end. This shorter distance allows further shifting of the CVT's and overdrive.

By shaving the spacer, we are not shifting the whole gearing - only adding an 'overdrive'

[Dandy Dan]

I kind of agree...when you shorten the spacer you are 'narrowing the distance the primary needs to close to squeeze the belt' and you are correct that in the mid-range the clutches kinda adapt and you can just use lighter rollers too to get the midrange the same.

What I'm trying to say is that when you shorten the spacer, you start off from the line in a taller gear ratio because your belt is pinched. It's riding up a little even when you're stopped. If you just shave about 1mm off the spacer then it doesn't really do much here but if you take say 3mm off you'll easily notice you are starting off in a taller gear ratio and your 0-5mph times will become noticably more sluggish.

After you reach 5-10mph you can operate at the same gear ratios as before but you need slightly lighter roller weights to delay the upshifting so that your revs can catch up.

Maybe I should re-install my modified variator and post some RPM over time graphs of it vs. a stock variator.

[timberwolfmadcat]

dandydan said:

I kind of agree...when you shorten the spacer you are 'narrowing the distance the primary needs to close to squeeze the belt' and you are correct that in the mid-range the clutches kinda adapt and you can just use lighter rollers too to get the midrange the same.

What I'm trying to say is that when you shorten the spacer, you start off from the line in a taller gear ratio because your belt is pinched. It's riding up a little even when you're stopped. If you just shave about 1mm off the spacer then it doesn't really do much here but if you take say 3mm off you'll easily notice you are starting off in a taller gear ratio and your 0-5mph times will become noticably more sluggish.

After you reach 5-10mph you can operate at the same gear ratios as before but you need slightly lighter roller weights to delay the upshifting so that your revs can catch up.

Maybe I should re-install my modified variator and post some RPM over time graphs of it vs. a stock variator.

yeah, thats an easy 20 min job that would solve all this arguing

[Dandy Dan]

I'd do it but we got a new Mac and my dad hasn't installed windows on it yet so I can't run the Veypor software on my computer. I could do it and tell you guys the results but that doesn't pack near the punch that a nice graph does. Maybe in a couple weeks...

[jumpjunky]

dandydan said:

I kind of agree...when you shorten the spacer you are 'narrowing the distance the primary needs to close to squeeze the belt' and you are correct that in the mid-range the clutches kinda adapt and you can just use lighter rollers too to get the midrange the same.

What I'm trying to say is that when you shorten the spacer, you start off from the line in a taller gear ratio because your belt is pinched. It's riding up a little even when you're stopped. If you just shave about 1mm off the spacer then it doesn't really do much here but if you take say 3mm off you'll easily notice you are starting off in a taller gear ratio and your 0-5mph times will become noticably more sluggish.

After you reach 5-10mph you can operate at the same gear ratios as before but you need slightly lighter roller weights to delay the upshifting so that your revs can catch up.

Maybe I should re-install my modified variator and post some RPM over time graphs of it vs. a stock variator.

I disagree again - as long as you're not changing the angle of the sheave faces - you are not changing the ratio at take-off. The belt will still engage at the same spot on the primary face - it's just that the sheave didn't travel as far to the engagement spot.


The reason you leave 'slack' in the belt to sheave distance is to make up for manufacturing tolerance stackups in manufacturing of the belts and primary sheave faces. Ultimately, you want belt to face clearance to be 0. This helps with belt life as the primary doesn't 'slam' into the belt. By shortening the spacer, we're doing that - and get the benefit of the taller gearing on top.

Shortening the spacer will have NO affect on anything except top-end.

There's a good book if you wanna really brush up on CVT tuning. It's writen by Olav Aaen. It's geared toward snowmobiles, but it's the exact same theory here, only on a smaller scale. Most people who have read it agree - it's the CVT tuning Bible. You can find it on Amazon.

The basic idea of clutch tuning is to set the spring and rollers or flyweights in your primary (engine) clutch bring the engine to a specific RPM (hopefully right at peak HP). Then adjust the spring tension and ramp angles on the secondary (driven) clutch to get the shift characteristic you want. That shift characteristic is largely dependent on your personal preference and driving style. The theoretical ideal is a slight RPM peak at engagement, then flat at the peak HP out all the way though the shift-out phase with the RPM slowly climbing above the peak HP once you're shifted all the way out into overdrive. Again, that's theoretical... you may find that you never get there

[chanito]

This is a subject were both of you are right and both of you are wrong, in theory what DD say is wrong, as the cvt operating principle (as stated by Jump junky) is that at rest the belt will not start moving up until the speed of the engine reach the roll-off speed (the speed at which the clutch is spinning fast enough to engage) so if you narrow the front (driving) pulley it still will not do anything until this speed is reached. But space limitations, have put the belt in the front pulley with almost no slack (YES, THERE IS SLACK) so narrowing the front pulley by shortening the spacer makes the belt ride higher than it would at rolling speed, so What DD say is right.
I have been lucky enough to read some very informative material about CVT (hey i work for Nissan and they have them on the muranos, and now on Maximas, sentras and Altimas) and they are very simple transmissions, sadly most info i found is about 2-cycle engines, that have a very narrow torque band, so roll speed is WAY higher than what we have on the ruckus, our roll-off speed is 3500 rpms and the belt goes thru the full motion between 6 to 7 thousand rpms, on the other hand most 2 cycles roll speed is in the mid 5Ks and it goes thru the full range also between 6 to 7 Ks ( that is why the narrowing is more noticeable on a ruckus than say a zuma) but luckily for us the big power band of our power-plant give us way more room to play, but the changes are not as dramatic or impressive.
I am a guy who really have to be convince that something is worth the money before going out and buying, and in "my personal opinion" shortening the stock variator is an easy rewarding mod with no need to spend extra money. I still have my stock variator with a shortened spacer and a grinded nose and i am very happy with it

[ZOOMER46]

uh oh, what have i started..........

actually this has been very productive banter on this one, ;D

but is chanito saying that all i had to do to gain top speed was
trim the length off my spacer???!!!!

i should of measured my new and old spacers,
tho,
i guess myzoomer spacer could be shorter than yours
,cos ours are very slow on topspeed from new.i.e 28mph.

as for my results on the polini i did a write up in the new
metro gears column.

[suprtek]

I appreciate the info in this thread. I was considering doing this mod. I decided against it because a reduction in low end acceleration is unacceptable to me. Since I am one of the "big" guys at over 200 pounds, I would notice this lack of acceleration even more. I guess I will have to buy a polini if I decide I really want more speed. Great info guys! ;D

[Dandy Dan]

jumpjunky said:

The belt will still engage at the same spot on the primary face - it's just that the sheave didn't travel as far to the engagement spot. Ultimately, you want belt to face clearance to be 0. By shortening the spacer, we're doing that - and get the benefit of the taller gearing on top. Shortening the spacer will have NO affect on anything except top-end.

I understand what you mean when you talk about slack and how shortening the spacer just reduces that and ultimately we do want it to be virtually zero. The catch however is that the slack is virtually zero with a stock variator and shortening the spacer gives you negative slack so your belt never drops all the way down. That's why what your saying about reducing the slack makes sense in theory but in reality there isn't extra slack to get rid of.

This is clearly observable if you actually shorten your spacer significantly and go for a ride. When I shortened my spacer 1mm there wasn't much of a difference off the line or on the top end so I shaved another 2mm off and then I did gain a few mph on the top end but my 0-5mph times were miserable. There was an easily noticable lag for about 2 seconds before I was making any sort of power. I imagine Chanito can vouch for something similar (although perhaps not as drastic).

I don't think there's any room to shorten the spacer and just take up slack because anyone who's reassembled their variator can tell you that even with a stock variator, you're pinching the belt in there when you reassemble the variator. This zero slack is the main cause of a lot of variator problems because people reassembling their variator think they have the variator on tight but really they're just pinching the belt and feeling that resistance. Now that I think about how much the belt is being pinched with a stock variator, there may be some potential off the line gains by using a longer spacer. I can't even get my variator on snug without working the belt down into the rear clutch so that I can let the belt ride up in the front while I tighten the variator nut.

Shortening the spacer is a good mod if you need more top end and off the line speed isn't important to you but if you want a significant gain up top you should be prepared for a bit of a hit on the low end.

[jumpjunky]

chanito said:

anything until this speed is reached. But space limitations, have put the belt in the front pulley with almost no slack (YES, THERE IS SLACK) so narrowing the front pulley by shortening the spacer makes the belt ride higher than it would at rolling speed, so What DD say is right.

This 'slack' is called belt defelction. Deflection is dictated by 2 things - center-to-center distance (which we're not changing) and the seconday. One can change the deflection by how far the belt rides up or down in the secondary. On these models, we have no adjustment.

Chanito - I disagree with your enagement theory. Again, the belt is riding down on the shaft of the primary when still. When we 'gas' it, we spin the rpm up until the centrifigual force of the rollers overcomes the spring pressure. At this RPM, the moveable sheave starts moving and 'catches' the belt. As long as the belt is NOT engaged at rest (with stock or modified spacer), the belt still enages at the exact same spot on the moveable sheave. The sheave just had less distance to get there with the modified spacer.

Gotta love keyboard racing

[Dandy Dan]

jumpjunky said:

When we 'gas' it, we spin the rpm up until the centrifigual force of the rollers overcomes the spring pressure. At this RPM, the moveable sheave starts moving and 'catches' the belt.

No our scooters don't engage like this. The 'centrifugal force of the rollers' has nothing to do with the engagement point. The variator and belt are ALWAYS engaged together. The engagement doesn't happen when the plates squeeze the belt. Regardless of what roller weights and clutch compression spring you're using, your scoot will still engage at 4000 RPM. You can even take the roller weights completely out of your variator your drive unit would still engage @ 4000 RPM and you could still go for a drive, just your variator just wouldn't upshift so you'd redline at 20mph. I've done it....

The reason the rear wheel is not connected to the engine is not because the variator hasn't squeezed the belt. Rather it's because there are pads back in the clutch that operate like brake shoes and when the clutch spins fast enough these pads fly outwards and engage to the inside of the clutch bell. It's just like a drum brake except centripetal force causes it to engage instead of pulling a lever. Our rear clutches spin around the drive shaft and when the clutch pads engage the clutch and driveshaft are connected and that's what completes the engagement.

That's why at the point of engagement your variator does not have to be at it's lowest gear ratio but rather you could shorten the spacer way up and start off in your tallest possible gear ratio if you wanted.

[chanito]

jumpjunky said:

chanito said:

anything until this speed is reached. But space limitations, have put the belt in the front pulley with almost no slack (YES, THERE IS SLACK) so narrowing the front pulley by shortening the spacer makes the belt ride higher than it would at rolling speed, so What DD say is right.

Gotta love keyboard racing

I think you are confusing our variator transmissions, the front or driving pulley only have the weight or rollers that push the belt outward changing the front ratio. The rear or driven pulley have the centrifugal clutch and the loading spring, the front pulley is always driving the belt and they are in constant engagement, but the rear has a centrifugal clutch that allows the rear pulley to transfer movement to the rear wheel, but i think DD has explained it better ;D

[ZOOMER46]

so to summarise,shaving some length off the spacer in the front variator
will give you a higher pullaway point or gearing and will give you a potentially
higher top speed(if you could pull that ratio).
put am i right in saying that pretty much the whole time you would
be pulling a higher ratio than normal?
for the revs being used?

[puttingalong2]

I think I know where jumpjunky is comming from. He refered to Aaen's book on clutch tuning which is more geared towards a snowmobile type CVT system. That type of system does not have a centrifugal clutch like our scooters, but rather it engages when the primary clutch (variator) starts closing, and grabbing the belt. What he is describing is correct for that type of transmission, but the subtle differences of the honda system makes what he is trying to describe not applicable. I had a hard time getting around this when I first got my scoot, and I think once he cracks his open, and really watched it work he will realize what you guys are getting at. We should all be happy our systems are so simple, because a snowmobile CVT has literaly thousands of tuning options, where we basicly have a few variator weights to choose from, and three or so springs to swap in the driven clutch.

[Dandy Dan]

zoomer46 said:

so to summarise,shaving some length off the spacer in the front variator
will give you a higher pullaway point or gearing and will give you a potentially
higher top speed(if you could pull that ratio).
put am i right in saying that pretty much the whole time you would
be pulling a higher ratio than normal?
for the revs being used?

Yeah sounds right....you start off taller and you end up taller but you can save the middle range by using lighter rollers. I don't think you need to worry about being geared taller though zoomer46 since you already have a Polini and the Met gears.