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Post by dhmtbgreg80303 on Jul 18, 2018 9:54:03 GMT -5
Hi, I just recently bought my first scooter from a college kid for $60. It wasn't running, but a new vaccuum line on the petcock, new intake manifold, and a battery charge had it started up and running great. I think she just had zero mechanical knowledge which is why she let it go for so cheap. Now the problem I'm running into is extremely slow acceleration from a stop. I come from the motocross world, and it felt very similar to a slipping clutch.
Based on some other posts, I took the clutch bell off and sanded down the 3 glazed fiber pads, but didn't see any improvement. In my experience with dirtbikes, this is when I would replace the clutch fiber plates, so I'm thinking replace the whole clutch for like $27 from Amazon, but I'm not super familiar with the CVT system.
Is the best course to replace the clutch assembly with a new one? Or can I get heavier springs? Lighter variator weights? New Belt? It seems like there's plenty of material left on the fiber pads. I'm trying to avoid spending too much to replace the whole system, so I'm looking for the biggest difference for the least amount of money. Top speed seems pretty standard, so i don't want to trade top speed for acceleration.
Thanks for any help!
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Post by tortoise2 on Jul 18, 2018 11:10:57 GMT -5
slow acceleration from a stop Check if variator weights are oriented properly in the ramps. Might also consider a set of 5 gram sliders and slides. |
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Post by dhmtbgreg80303 on Jul 18, 2018 12:50:57 GMT -5
If I get the slider weights, do I need the slides? I also see 5g roller weights, not sure if these do the same thing
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 18, 2018 13:19:46 GMT -5
No, they are totally different. Also, see 90GTVert's great video on how to tune your cvt. It will save you a lot of time, and money. You can not really just pick out a roller or slider weight out of thin air that will work with all scooters and riders. It is a process. Depending upon what clutch I have installed, I have used anywhere from 4 gram sliders up to the 6.5 gram sliders i am using now. Same scoot, same belt, I am the same weight (give or take, ha ha) and I ride the same route to and from work. The object is to get it to hold a constant rpm as close to the power band rpm as you can and have it stay there from 0-top end. Once you get it perfect, it will drift around as the belt wears and the clutch springs get a little softer from heat, etc.
Search on this site for the difference between sliders and rollers and you will see a nice animation of how they can give you a little lower 1st gear and a bit higher top gear. I have used sliders shortly after getting my scooter because they perform better, in my opinion, and they last longer. Rollers can get flat spots which really messes with the cvt action.
Bill
EDIT:
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Post by dhmtbgreg80303 on Jul 19, 2018 11:42:47 GMT -5
Thanks PirateLabs! Awesome video, lots of info. I was trying to keep it cheap, but it looks like investing in some different jets, springs, and sliders at a minimum will be needed.
One more question: The odometer shows 746 miles, and i know it's likely been treated like absolute shit over that time. Is that a normal interval to replace the clutch? So far I've sanded down the fiber and roughed up the inside of the bell and seen a bit of improvement, but wondering if replacing it will have any benefit.
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Post by GrumpyUnk on Jul 19, 2018 13:10:11 GMT -5
If it does not engage until the rpms are higher than desired, or seems to slip, it's possible the springs are stronger than desired, keeping the 'shoes' from rubbing on the inner diameter of the clutch bell with enough force to 'lock up'. The contra spring that pushes the clutch pulley sides together(contra the variator demand to pull them apart by making its pulley bigger) can keep the engine in lower gear if it is too strong, denying the 'pull' of the variator. It may keep the clutch pulley 'big', forcing lower gear.
There are three levels of clutch spring & contra spring, to my knowledge, generally sold in 'sets' of 3 clutch springs & one contra. The contra spring can lose its tension over time and become weaker as it loses tension. That should(?) lead to the variator forcing upshift sooner... I think.
tom
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Post by pinkscoot on Jul 19, 2018 13:47:01 GMT -5
How thick are the clutch pads? 745 on the odometer is low for needing a new clutch, belt or rollers, but look anyway. Also check the thickness and wear of the belt and see how close to spec it is. See if the rollers are flat and weigh them. A 50cc 4 stroke engine is no speed demon so it may all be good. do a speed run 0-30 and let us know.
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Post by dhmtbgreg80303 on Jul 20, 2018 11:30:44 GMT -5
I don't have an accurate scale to weigh the rollers. My food scale showed 4 grams but i don't think it's accurate that low. Also no flat spots in the current rollers and they were oriented correctly in the slots. I ordered some 5 gram Dr. pulley rollers before i knew about the slider difference, so I'll weigh those and see what they say to get an idea of the scale accuracy.
Clutch fibers look pretty thick now, and they're not glazed after roughing them. I also got some 100 grit sandpaper and re-roughed the bell. I'll do a 0-30 test once I get the new rollers in and with the old ones and see how they work. I think at this point my order of operations is get the rollers right, then check the springs, then get a new clutch if necessary.
pinkscoot makes a good point, I'm used to much bigger engines with gears and manual clutches, so this "slow" acceleration might just be a feature of the scooter i'm not used to. I found a local scooter shop so I might have a tech ride it and see if anything feels out of the ordinary. Also try out some 5g sliders if I'm able to test and return.
One question on the Contra and 3 individual springs, just so I understand: If the 3 springs are stronger than the contra springs, the front variator will upshift and/or rear pulley will downshift before the clutch engages. So basically like starting a motorcycle in 2nd or 3rd gear. So if I get either a higher RPM Contra spring to match the 3 springs, or lower RPM 3 springs, it should engage the clutch in "1st gear". Does that all sound right? And if that's right, will lower weight sliders keep the front variator from upshifting until higher RPM's?
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Post by dhmtbgreg80303 on Jul 20, 2018 11:45:56 GMT -5
Actually, found a 1k RPM contra spring on ebay for $6 and I'm impatient, so gonna put that in with the lighter weights and see if that helps. I think I'm finally understanding the CVT. Just need to keep it from "shifting" up before the RPM's get high enough to engage the clutch. So the combo of lighter weights keeping the front pully from closing and stronger contra to keep the rear from opening should keep it in "1st" until the clutch engages.
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Post by dhmtbgreg80303 on Jul 25, 2018 10:18:03 GMT -5
Turns out my stock rollers were 5g. Had to go to a weed dispensary to use an accurate scale, but they came in at 4.99 grams. Got the contra spring in, so as soon as I'm able to get the main clutch nut off I'll check that out.
Also, went to the local store and the guys lack of knowledge had me shaking my head and walking out. He said they don't sell sliders because they "ruin engines unless you check them every time you ride". Then said since there's 15% less air at elevation the engine is putting out 15% less power. I told him different jetting or air filter would fix this, since every other single cylinder engine in CO still runs and puts out power, but he wasn't convinced. He tried to sell me a 150cc upgrade kit since it was "the only way to get better acceleration".
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Post by GrumpyUnk on Jul 26, 2018 8:46:32 GMT -5
The only thing I can assuredly say is that all engines lose power(including turbo or other) due to the scientific fact that air is less dense at altitude. You just cannot get the same 'burn' or 'thermal expansion' at altitude as at sea level because you cannot burn as much fuel. Even with a turbo, the air coming into it to be squeezed is still less dense, so it cannot stuff as much as at sea level.
That said, yapping about checking rollers or sliders every time is about as logical as changing the air in your tire when moving from one state to another.
tom
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Moat
Scoot Member
Posts: 88
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Post by Moat on Jul 26, 2018 11:23:31 GMT -5
Not so!! Turbocharged/supercharged systems often have wastegates/boost controllers that can easily compensate for increases in altitude by increasing the amount of boost (manifold pressure) accordingly. This is known as "turbo normalizing" when it maintains sea level manifold pressure.
Turbo/supercharged WWII-era piston aircraft had the ability to call on "emergency" or "combat" power at very high altitudes during life-threatening/battle situations - essentially over-boosting for a limited amount of time (just a few minutes, or risk engine damage/failure) and developing power well beyond for which the engine was normally rated @ sea level (takeoff or continuous power ratings).
Bob |
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Post by GrumpyUnk on Jul 27, 2018 13:27:57 GMT -5
moat, I don't particularly care about WWII compound turbo charged aircraft engines. I know about them.
The point was that changing the jetting will not compensate for altitude. Turbos still have to work harder to get the same performance as at sea level. Jets will not compensate. The 'tech' that was blabbing is ignorant, and I was trying to correct a misrepresentation that jets will do the trick. They won't.
tom
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Moat
Scoot Member
Posts: 88
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Post by Moat on Jul 27, 2018 17:14:52 GMT -5
Wait... what?? The "babble" you referenced above was about slider/roller weight, and is not entirely "ignorant" as you suggest - tweaking roller weight might indeed help in maximizing acceleration/performance of a scoot hindered by altitude-related power loss. And it's common knowledge that a naturally-aspirated, carbureted engine needs to be jetted according to it's operating altitude in order to run optimally. If you know about aircraft engines as you claim, then you also know they incorporate manual mixture controls for that exact reason. So... wait... what?? Bob
(edit) - Ahh, now I see - yes the "check sliders every time you ride" thing is indeed nonsense. But the OP was talking about re-jetting (which could very well be a good idea), and the "tech" was also correct in the altitude-related power loss thing; these are two completely different things -
1) Power loss due to decreased air density at altitude (unavoidable without turbo/supercharger), and...
2) Power loss due to the increasingly richer mixture that carburetors inherently deliver as altitude increases.
Nothing realistic can be done about #1, but some of altitude's power loss can be recovered with careful attention paid to #2 - jetting leaner.
And lighter rollers/sliders could help as well.
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Post by dhmtbgreg80303 on Aug 12, 2018 18:23:14 GMT -5
So it's been a while, but I finally got the tools I needed to remove the clutch nut. I bought a new clutch, put in a 1k contra spring, and some 1k clutch springs and takeoff is embarrasingly slow. I'm going to try the 1k contra with stock clutch springs next, I think the higher RPM's needed to engage the clutch is cancelling out the heavier contra spring. Does that sound like the right next step?
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