Please help me understand CVT's By looker (Read 2,892 times)

[looker]

Hi guys,
I'm geting to know my scooter now-a-days, how things work, how to change things etc etc...I have a Peugeot Sum Up 125 gy6 based scooter (QMI152)

I had a little problem the other day when I pulled away from the traffic lights, engined revved up fine but the scoot pulled away slower than normal. Got up to speed o.k. and the problem went away after a short while (pulled off the main drag and went round some quiet streets stopping and starting).

Pulled the belt cover off when I got home to see if I could find anything obvious. Belt was a bit loose and about 18.5mm wide, I think the service life is 19mm, so put a new belt on. While I was at it I took the variator and clutch off which both seemed fine apart from the bell. It seems to have uneven wear on the inner surface, to me it looks as though the tack welds that hold a metal ring on the outside of it have slightly distorted the overall roundness of the inner surface. Could this cause clutch slip?
I sometimes get a judder form the trans when moving at slow speeds, though it has previously disapeared after a belt change.
Am I missing something? do you think.

The rollers looked fine, they've done about 2500 miles if memory serves, the only thing I noticed was the ramp plate is a little stiff moving up the basket for the first few mil. Could'nt see any obvious flat spots on the rollers. Is there a general service life to rollers, or just change them when they wear out?
Basket is clean and free of crud, the only lubing I've done to it was an application of graphite powder.

A few things I'm having trouble understanding, roller weights for one. Lighter ones give better pick-up/acceleration, heavier ones give a better top speed, at the cost of acceleration. Does this mean lighter ones will reduce the top speed?
Also, mixing rollers of different weight. Say, 3x12g and 3x14g for instance, how does this work? Won't the heavier rollers negate the lighter ones on accleration, or am I missing something again?

And clutch springs, what's the RPM rating about? This time of year my scoot needs a higher tick over (about 1800RPM) otherwise it cuts out a lot when cold. If I had 1500RPM springs on the clutch shoes, would the rear wheel be trying to turn all the time at tick over? And the big spring inside the clutch assembly, how does the RPM rating work on this?

Sorry to prattle on, but I'm looking into toying with the roller weights. The scoot seems to be fine overall, pulling away nicely and giving about 55mph indicated on the speedo, 65mph on a slight downhill with no headwind but pulling about 9000RPM.
I've no GPS system to confirm these are actual speeds, the only way I have to verify the accuracy of the speedo is following behind a vehicle as it goes past a speed camera at say 30mph or 40mph (we have looooooads of speed cameras here) and the speedo seems fairly accurate.

What I am looking for is a slightly better pull away from stand still and those times when I'm passing stationary cars at red lights and the light turns green and I throttle up. Is finding a cheapish set of different weight rollers and toying around with the variator to find the best weight a good thing to try? And then getting some quality rollers at that weight?

Oh, one more thing, the ramp plate appears as though it's cut and formed from a single piece, this seems to have left some 'edges' to one side of the plate which in turn seems to affect the fit of the guide bushes. I only have a very small amount of funds for the scoot at the mo, but I'm willing to pay out for a whole new variator if it will improve things. Any ideas on a good make. Postage from the States is quite a lot of bucks to here, so I'll need to look around other online stores for a good price.

Any tips on the clutch front would be aprreciated too.

Sorry, just remembered, riding habits of the bike are....open roads mainly into London (though I tend to stay off the freeway style dual carriage way for the most part) and then it's onto the streets of London with lots of stop/start riding. I want to retain the 50mph or so speed of the scoot for the main roads, but a bit of nippyness around town. Is it one or the other, am I dreaming to have both?

Thanks for reading and sorry to go on for so long,
Mike

[Alleyoop]

Hi Looker,
Lets tackle the Cold idleing, Adjust your Air/Fuel Mixture RICHEN it, with the Colder weather the engines need more fuel due to the dense air. Adjust your Air/Fuel Mixture When the Engine is HOT to get the Highest RPMS out of it , then re-set your Idle.

Rollers:
Lighter Rollers will Keep the Belt in the Lower part of the Variator Longer and Requires Higher RPMS to Squeeze the Variator to move the belt higher.
Heavier Rollers Require Less RPMS to Squeeze the Variator to move the belt higher.

RPM CHANGES WITH WEIGHTS:
Rollers: For Every Gram it will change your RPMS by 500-600 up or down.
Sliders: For Every Gram it will change your RPMS by 250-350 up or down.

So with the weights you can change at what RPMS you want to be running at WOT or in between.

Find out what Gram Weights you currently have and depending on how you want the Scoot to ride you can I would buy TWO sets of Weights:
If you want more exceleration and you have say 13gram weights:
I would get 11s and 12s;
Then you have many possible combinations to try:
1. All 11s
2. All 12s
3. 3-11s 3-12s= 11.5
4. 3-12s 3-13s= 12.5
NOTE:
When using combinations Example: you put 1 say 11 then the next slot a 12 and so on. You do not put the different weights all together.

Once you find the Roller Weight Combination you like then you can get 1 Gram Heavier Sliders to Replace the Rollers. That will be just about the Same Rpms as you were with the Rollers Plus with the Sliders you will get a 1-2 mph higher speed than with the Rollers.

The Clutch:
Slipping can be caused by the Belt being worn(like you found on yours).
Clutch Pads worn down or not all three pads making good contact with the Bell.
Distorted Bell

Contra Springs:
The stronger the spring the more power is needed to open it up so the belt can slid down for higher speeds(require more rpms). Also they can put a lot of streess on the belts and also get them really hot. If you put in Stronger Springs the way you drive around will change, because you will always have to keep your RPMS up. Think of them as when you see the Hot Rods at the Dragstrip, you hold the Clutch in and REV it up and Pop the Clutch, great take off but you you need more RPMS.
Hope this helps
Alleyoop

[looker]

Alleyoop,
many thanks

Cold idleing:
I'll give that a go, I had'nt considered playing with the mixture as the plugs I've changed out had looked in good condition and about the right colour for a used plug.

Rollers:
I think the standard ones are 14 gram, I have a set of digital scales coming so will be able to tell when that arrives.
If I'm reading you right, when mixing 2 different sized weights, put them in...say....11g, then 12g...11, 12...11, 12? that's how I imagined doing it. If that works out to be a good weight choice and I buy some decent 11.5g rollers, will the variator not work differently due to all the rollers being the same weight? Do you see what I mean? I'm having trouble getting my head round using different weight rollers at one time in the variator.

Clutch:
I'm hoping it was the belt causing the problem, hav'nt been out on the scoot since I changed it.
Clutch pads do look o.k. I think the bell may be distorted and causing, or at least adding to the juddering problem. Could be that it's not that bad untill the belt starts to wear and then the 2 combine to cause a noticable judder at slow speeds.

Contra spring:
so the higher the RPM rating, the stronger the spring. Same for the clutch shoe springs? and the higher the RPM rating, the more revs you need to engage the clutch shoes? and the contra to open up the pulley and change the gear ratio?

I think I'm getting the gist of it now

Many thanks for taking the time to read my long winded post and make a reply, really appreciate it,
Mike

[Alleyoop]

Looker,
If the roller weight combo you like happens to be in the .5 combo it is not a problem to go with 1 gram heavier Slider Weights. You will not notice the difference only in the smoothness of exceleration with the Sliders.

And for the rest you got it my man. You can also JUST buy the Bell to replace yours if that is not looking good.
Good Luck,
Alleyoop

[looker]

Alleyoop,
thanks again, you're a tremendous help
If you don't mind, with the lighter weights, will I lose top end speed, or it will just take longer to get there? Or will the difference be negligable?
I'm guessing from you're previous post that it will take more revs to reach the same top speed, efectively losing a bit at the top to keep the engine from reving it's nuts off?

Cheers,
Mike

[Alleyoop]

Looker,
I don't know what your revs are at right now, but on your tach it should be marked where the Red line starts. Usually around 8000 rpms on most 4 Stroke scoots. I would keep whatever you decide under the Redline Rpms. If you like what you have there or want to go 1 Gram Heavier to Lower your RPMS but still have good Low Speed and Mid-range exceleration Then you may have to get a little Heavier Contra Spring I would not go more than the 1500. That will help in keeping the Belt lower on the Variator with heavier weights.

That is why you have to find the Right Combo because to much one way you loose top speed and the other way you may loose exceleration speed. So you have to find a mid point where you keep the top end but good exceleration.
Alleyoop

[looker]

Alleyoop,
I see what you're saying
I'm not too sure, but I think it's pulling about 8000 rpm to hit the 50 or so mph mark. I'll make a mental note of that next time I get out.
I think I'll start by waiting for the scales to arrive so I know for sure what rollers I have in there, then try some other ones a gram or so lighter. If that gives me what I'm looking for without losing too much top end, sorted
If I do need to change the contra spring, is there any way to tell what the rating is of the one that's in there? I don't want to be changing it if it has the same rated one in there.

This leaves me with a dilemma, if I end up buying parts seperately, and need to buy quite a few, am I better off buying some sort of tuning kit to start with? Hmmm...decisions decisions.. is it o.k. to link to ebay on this forum so I can give you an idea of what I'm looking at and if it's any good or a pile of poo?

Cheers,
Mike

[Bashan]

Link away Mike, and we're not scared of poo! However, you might want to also peruse one of our banner folk's website. Just click on KidNMe when it comes up at the top of the site. You can also e-mail Tom about his wares and CVTs in general, that's one of his specialties. He's a very nice guy and won't try to pressure you into buying anything. Just tell him your from Scooter Doc and you'll get special treatment . Rich

[looker]

Thanks Rich,
epay link, cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_trksid=p4712.m2000054&item=330498987405&viewitem=
Anyone seen/used this kit before?
Looks like a fairly good piece of kit to me, but what do I know
All I'd need then would be a new bell, kidnme have a nice ally one. I've been looking at the Dr pulley hit clutch too, but that's way out of my price range at the mo, maybe in the future once the scoot has served it's work purpose and becomes a summer leisure vehicle ;D

Cheers,
Mike

[Bong]

Yes, THANK YOU ALLEY!!! your roller/slider weight explanation was very informative. Never thought of mixing weights. You rock!!

[Alleyoop]

BongKaos,
Thanks for the Kudos:)

Looker:
That setup on ebay looks like a good deal, The ONLY thing is ASK THE SELLER if the VARIATOR is 115mm if its NOT then DO NOT BUY IT.

What you want is a VARIATOR that is the SAME DIAMETER as your FAN PLATE. And on the 150s the Fan Plate is usually 115MM but the Variator is only either 105-107mm in Diameter. So what that means is the Belt will only go as high as the Vairator. Now with a Variator that is the same size as the 115mm then you have the possibility of getting the Belt to go about 3/8 higher(means more top end speed) 3-5mph.
Alleyoop

[looker]

alleyoop, you're a real star bud
My scoot is a 125cc. These and the 150's seem to share a lot of the same parts size wise. I'm gonna take the scoot out soon for a ride to see if the new belt has solved the problem. Gonna strip the trans down when I get back home and takes some measurements. I think I really need a new bell, scrappydog have a nice drilled one for 40 bucks, hopefully he'll be willing to post to the u.k.

What do you think the black coating is inside that variator? could it be Teflon maybe? I've read that it comes off after a while gumming up the rollers. Does look like a good deal though. The kit would give me 4 sets of rollers about the 13g mark, a new variator assembly which could be kept for a spare at least, a new clutch assy with spare springs and a contra spring.
Buying all that seperately would cost a lot more, and I'm sure it will all get used over the working life of the scoot.

Any idea what kind of mileage these scoots are capable of in general? 30,000...40,000....more? I know it depends on how it's looked after. I change the oil about every 1500 miles, and the transfer box oil 'bout 2000, 2500. It's not riden particularly hard.

Many thanks again,
Mike

[Alleyoop]

Looker,
The black coating is Teflon, but it does start to come off and gum up your weights. But you can clean it up with some fine emery cloth. Yes, anytime you can get an entire set for less money is a good idea just to have spare parts. Mileage on the scoots you are correct if taken care of they are capable of 30-40K.
Well if Scrappydog does not post to U.K Buggyspartsnw.com does, I have gotten a lot of things from him. I just put on an Entire Clutch I bought from him for $59.95. www.buggypartsnw.com/home?page=shop.product_details&flypage=flypage.tpl&product_id=309&category_id=16
Alleyoop

[looker]

well s**t on me
Took the scoot out for a ride, less than 10 miles, still doing the same thing, but seems to be once it's warmed up.
Also noticed that when you come off the throttle and coast to a stop, as the revs get down to just under 4000 it's as though there is a brakeing effect going on somewhere, when the revs get just below 3000 it disappears
That's not the end of it, thought I'd cut the drive short and head home as the problem was still there, got a few miles from home and there seemed to be a 'shaking' going on, another half mile and I lost all drive. I'm assuming the belt has snapped as there was no clanging or banging (from anything metallic letting go), just the engine revs shot up and drive went. Killed the engine and pulled over. Had to push it the other 2 miles home, uphill at first, then thankfully down hill for the last mile.
I'm knackered, not been home long, sweating like a pig even though it's cold so jumped in the shower and then sat down with a coffee to write this. Gonna go out to the garage and pull it apart again. I'm thinking it's the clutch got overheated and bye bye new belt. Only put the bugger on the other day, that's a new belt going in the garbage

I'll take some pics and start a new thread once I know what's what. Not that I don't like talking to ya alley, but hopefully I'll get some others replying

Many thanks bud,
Mike.

[Alleyoop]

Looker,
Not a problem I chimed in because nobody was responding to you, I will take a nap.
Alleyoop