KymcoForum.com
General => Technical | How To => Topic started by: Parkmice on April 17, 2020, 06:42:03 AM
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Hi all,
This is my first post, and I need some advice. I'm a motorcycle technician but don't have any experience with scooter CVT's. I do have some experience with snowmobile CVTs though, so I have probably a basic understanding of what does what and why.
I'm working on my buddy's People 50 2t. It showed up his multivator (I suspect the little cushions failed on the steel ramp plate, allowing the steel ramp plate to chew into the aluminum pulley half). I did some research, and decided that a Malossi Multivar would you be a good choice, because he lives in an area with some steep hills. So I ordered a Multivar kit (with white contra spring) and Malossi Kevlar belt to match from the local Kymco dealer.
I installed the parts yesterday, that wasn't happy with where the belt was writing on the driven pulley. It rides about 12 mm lower than the outer edge at rest. If you look in the attached picture, you can see this belt is even lower than the wear marks made by the stock belt He was running. on a snowmobile, we would be concerned about that because the vehicle would not have low enough gearing to give snappy acceleration from a stop. Am I concerned about nothing?
According to the packaging on the belt, the Malossi #6111153 belt is 734mm with a 30 degree pitch. I think I read somewhere that the stock belt Kymco uses (#23100-KEB7-9000) is 748mm and 28 degree pitch. I could see how a 14 mm shorter belt would be forced to run lower in the pulley. Am I right about the length of the stock belt? I had the dealer go back and double check the part numbers, and according to the Malossi catalog, these are correct for the 2t People 50.
What should I do? Run it?
Thanks in advance!
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I do not know the belt spec for that bike but the correct length is crucial. I short belt will be heated by the increased friction and stress and is at risk of breaking.
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On scooters the belt width and length are very important. As the length is not going to change with wear, cut a strip of paper to go around the outside diameter of the original belt, and mark it where it meets. Take that paper strip to the aftermarket belt and check to see if the length is the same.
I've always found it best to get OEM belts when available.
The belt should run very close to the outer diameter edge of the torque driver at idle. If the belt is the correct length and it does not, it means the variator is not opened up enough for some reason to allow the belt to drop to the boss.
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+1
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On scooters the belt width and length are very important. As the length is not going to change with wear, cut a strip of paper to go around the outside diameter of the original belt, and mark it where it meets. Take that paper strip to the aftermarket belt and check to see if the length is the same.
I've always found it best to get OEM belts when available.
The belt should run very close to the outer diameter edge of the torque driver at idle. If the belt is the correct length and it does not, it means the variator is not opened up enough for some reason to allow the belt to drop to the boss.
Yes, agreed. Could you please comment, based on your experience, on the picture I posted? Doesn't the belt appear too short? The belt is down all the way on the boss at the variator and like 12mm from the outer edge of the driven pulley as shown in the pic.
Kymco doesn't have a published spec forrequired belt legnth. The OEM belt I removed measures 736mm and was worn to 16.8mm wide. This Malossi is 734mm and according to Malossi is correct. Gates and other belt manufacturers show 748mm belt by application
My feeling is that if I were to buy a 748mm belt it would ride all the way up in the driven, and still sit down on the variator boss. Does anyone here have experience with this kind of thing?
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I looked at the Malossi fitment for the belt you posted, and it looks as if it is the correct one for a variety of the Kymco 50cc models. Looking at the Kymco parts fiche, the same belt fits a variety of models also.
Assuming it was the OEM belt that came off, and they were about the same length it should be OK.
Yeah, it doesn't look right - but how does it run? Bog on takeoff?
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Yes it felt to me a little boggy on takeoff. It's my buddy's bike, though, and I put on some weight lately lol. So maybe I'm wrong about it.
I had two goals with this project, the first being to replace the broken variator, the second being to give him better performance up hills because he lives in a hilly area. It will be faster on the top end regardless because I got rid of his limited boss.
Maybe I'll juat buy a $30 Gates belt for the sake of experimentation.
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Most scooters have a pretty good take-off acceleration from standing stop. So if there is a bog, something is out of tune.
You said that you got rid of the restricted boss, so that means you had another. For sure the original Kymco one?
Double check to see that the belt sits all the way down to the boss at idle. The drive faces being even a millimeter too close will effect the operation.
I guess after checking it all out, trying the longer belt won't hurt. You will know right away if it will work.
A number of years back I changed out the belt on my Zuma. I don't remember the brand of the belt that went on - but it just caused the the scoot to perform poorly. Very bad acceleration and operation. Cut the scoot ride short and went and changed the belt out to the one that was on there. That's when I learned to stay with OEM belts.
You buddy have this scoot since new? If not no telling what may have been in there....
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Most scooters have a pretty good take-off acceleration from standing stop. So if there is a bog, something is out of tune.
You said that you got rid of the restricted boss, so that means you had another. For sure the original Kymco one?
Double check to see that the belt sits all the way down to the boss at idle. The drive faces being even a millimeter too close will effect the operation.
I guess after checking it all out, trying the longer belt won't hurt. You will know right away if it will work.
A number of years back I changed out the belt on my Zuma. I don't remember the brand of the belt that went on - but it just caused the the scoot to perform poorly. Very bad acceleration and operation. Cut the scoot ride short and went and changed the belt out to the one that was on there. That's when I learned to stay with OEM belts.
You buddy have this scoot since new? If not no telling what may have been in there....
Yes, the Malossi Multivar comes with a new boss and a white contra spring, so I guess I was expecting this to be kind of install & go lol. Now that I think about it, I didn't measure the length before I installed the boss. Maybe I need to shim it out a little. But I'm pretty sure the belt rides down all the way in the variator. I ran a sharpie test today, marked the variator from the boss all the way to the outside edge. After a mile run ALL the sharpie was gone from the boss to the very outside. Maybe I'll try shimming a little bit to gain some extra belt height at the driven pulley while I'm waiting for my 748 experimental belt to show up. I was impressed by this video:
https://youtu.be/z6bwq2Mq6p8
Although he wasn't the original owner, I removed a stock Kymco 23100-KEB6-9000 belt and the chewed up variator has Kymco stamped on the ramp plate. It was seriously damaged.
The bogginess might be to the new problem I found today: low compression! Only 60psi with the electric starter and 90psi when I kick as hard as I can. Tests were with a warm engine and throttle held all the way open.... I'll start a new thread for rebuild ideas I guess.
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it looks like the boss is to short,, or the washer spacer is missing in front of boss, or the belt is to wide, the belt should be almost on the boss, not driven by it , it is driven by the pulley , are you using sliders or rollers, I found Dr. pulleys sliders work well and last far longer, good luck let us know how it works out,
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1. I'll measure the boss legnth today.
2. As the scooter came to me, there was no washer in the stock variator at the end of the boss. The schematic in the Kymco manual doesn't show any washer either. Are you talking about a shim that I might add? If so, I'll be trying some shimming experiments later this week.
3. The belt is 18mm wide, which is to spec.
4. How do I measure belt distance to the boss? I have verified the belt rubs on the angled sheath of the variator all the way down to the boss, so in my mind it could be running hard on the boss. The belt is tight enough that this could be happening. I guess I could do a sharpie test on the boss, right?
5. I'm using the 9g rollers that came with the Malossi Multivar kit, as I'm assuming the white contra spring that came with the kit is matched to these rollers and the slope of the Multivar ramps & ramp plate.
I have a longer 748mm belt on the way, and am ordering a shim kit today, so later this week I should be able to run some more detailed experiments.
-Mark
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I was going to mention this to you before - now that you have seen that video this will make sense to you.
I have a 2 stroke Aprilia that I restored and rebuilt with all hot rod stuff. When tuning, it is difficult to know what is the real issue when things aren't "right". You may think a bog is from the carb tune, or the transmission, and chase your tail. After I had experimented with roller weights and carb tuning I could not get rid of a bog. Bought a new carb, thinking that would make a difference. Long story - after dinking around with scoot for over a year and never getting rid of an off-idle bog I pulled the variator off and added a shim that was maybe 1 or 1.5 millimeter thick between the boss and the drive plate. That was the ticket - scoot runs perfect now.
I had checked that belt and the distance between the drive faces and the boss several times and thought it was OK.
And I was no noob at this tuning stuff - had hopped up several 2 smokers before and had not run into this issue.
Live and learn. Hopefully the shims and the new belt will get you right.
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I was going to mention this to you before - now that you have seen that video this will make sense to you.
I have a 2 stroke Aprilia that I restored and rebuilt with all hot rod stuff. When tuning, it is difficult to know what is the real issue when things aren't "right". You may think a bog is from the carb tune, or the transmission, and chase your tail. After I had experimented with roller weights and carb tuning I could not get rid of a bog. Bought a new carb, thinking that would make a difference. Long story - after dinking around with scoot for over a year and never getting rid of an off-idle bog I pulled the variator off and added a shim that was maybe 1 or 1.5 millimeter thick between the boss and the drive plate. That was the ticket - scoot runs perfect now.
I had checked that belt and the distance between the drive faces and the boss several times and thought it was OK.
And I was no noob at this tuning stuff - had hopped up several 2 smokers before and had not run into this issue.
Live and learn. Hopefully the shims and the new belt will get you right.
Dan, glad to hear that helped. I haven't received shims or longer belt yet, but I did a sharpie test on my boss to see if the belt is actually touching the boss- it is. Rubbed all the sharpie off the boss in 3 minutes of idling. I know the belt shouldn't be rubbing the boss, right?
Also I noticed that the belt is so tight that (with the engine shut off) when I try to turn the driven pulley and hold the drive pulley, there is absolutely no slippage. I should be able to at least turn one pulley and the belt should have enough slack to allow some turning (with some amount of drag), right?
In my mind, adding a shim or two will not cause the belt to not run against the boss, only a longer belt would help with that, right?
-Mark
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There should never be slippage when the engine is shut off. The angular tension of the pulley sheaves keeps it locked in place. The belt can rub the boss and that's fine as long as it is not bearing enough load to make the belt loose grip with the pulley faces.
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There should never be slippage when the engine is shut off. The angular tension of the pulley sheaves keeps it locked in place. The belt can rub the boss and that's fine as long as it is not bearing enough load to make the belt loose grip with the pulley faces.
Ok, that's different from the snowmobile world, then. I guess that doesn't surprise me, because the snowmobile does not have a separate centrifugal clutch. They incorporate the clutching function into the drive pulley, in the form of some slack between the sheaves.
Given that I can verify contact on the boss and pulley sheaves all the way down via sharpie test, sounds like my shimming is probably perfect. It also sounds like an increase in belt length should get the belt out towards the outer edge of the driven pulley where I want it.
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I tend to disagree with that. I have noticed on mine that you can usually turn the torque driver and the belt will only have slight friction on the variator boss and drive faces. (upon shut-down).
Think about it - as soon as the engine revs up slightly the variator drive faces will close up and grab the belt. So a millimeter one way or the other can make a difference.
True, we are splitting hairs here.
That's why trying the shims will make sense. Be interesting to see how the shims and longer belt work out when they arrive.
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The clutch pulley faces are under constant pressure by spring tension. The pull of the belt presses the faces apart against the spring, therefore, when the belt losses torque(when no power is applied) the faces press together and press the belt with the same potential energy stored in the spring(minus loss) which maintains belt tension due to the v-belt's use of the equality of circular width. We may not be referring to the same part of the variator however.
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You are correct about the action of the Torque Driver or Driven Pulley as they are called, TBR125. That assembly is always under spring tension. It is the big pulley system that is close to the rear wheel, and the clutch is attached to it.
The variator - the pulleys at the crankshaft end - closes up and tightens on the belt with centrifical force only. That is the end of the transmission where the belt can be slightly "loose" when the engine is not running.
People will often call these things by the incorrect name, like clutch. It can be a bit confusing.
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For test purposes, I ordered a 748mm Gates belt and installed it. Just got back from a road test. It seemed to not big as badly when taking off from a stop. I topped out at 36mph according to my Waze app, and I had an eBay tach attached, showing about 6800-6900 rpm through shifting. The belt now sits almost all the way up in the driven pulley at rest, and my variator sharpie test shows the top maybe 3mm is not rubbing off, so I might be giving up a little top speed there. (Remember that with the 736mm belt I had absolutely no sharpie left on the variator anywhere).
I ended up not ordering or installing any shims. My thinking was that with the 736mm belt rubbing so much against the boss, that adding shims would probably not cause the belt to come away from the boss much, therefore not give the belt much room to expand out in the driven pulley. Also, I had pretty much perfect sharpie on the multivator, and thought shims would probably only serve to limit how far out on the multivator the belt could ride. Am I right about that?
The scoot is used in a hilly area. Who thinks I should stay with the 748mm belt? Who thinks I should go back to the 736 belt?
See attached pics:
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I'm going to be the odd man out in this discussion by saying it doesn't really matter which belt you use. It only takes 20 minutes to swap belts, so try one and if it runs up to speed stay with it. I've got a box of belts in my shop, and I just grab any belt that looks about right and install it. The variator adjusts to fit, so it's likely both belts will give the same result: 36mph. The most important pieces are the movable drive face, the rollers, the plate, and the slides.