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Post by Sir Scoots-A-Lot on Jul 21, 2018 17:47:58 GMT -5
I cannot rev mine up like that because the scooter shakes so bad, that it trying to "walk" when on the center stand. I have several nice parallel scrapes in the concrete from the center stand "walking" the bike. I do not notice the bike shaking or moving in the video. [/quote]
Wow Pepi...so you ran it on the center stand without a belt and still heard the noise? The clutch o guess would not be working with no belt...interesting....
I am wondering if our top speed noise could be from the variator, maybe exhaust restriction maybe, or some engine bearing such as con rod bearing or maybe even from the piston?
Pepi if your bike is shaking so bad when you rev it maybe your air/fuel mix is off and it is running rough? Though im not sure. If you post a video of it that may help people here to diagnose the issue. My centerstand doesn't raise my 12" back tire off the flat ground so I need to put it in the lawn and maybe dig out some dirt under the back tire and rev mine on the stand so I can make a video tomorrow.
I thought the other video I posted sounded like my top speed noise but when someone said it was fixed with a belt and clutch bell replacement I thought that was strange because I am not so sure this is causing the noise either
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pepi
Scoot Junior
Posts: 8
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Post by pepi on Jul 21, 2018 22:23:47 GMT -5
That is what I am thinking. The clutch is out of the picture, so could it be the variator? It is a brand new carb and I put it on out of the box and she fired right up. I will try to take a video tomorrow.
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Post by katt on Jul 21, 2018 22:37:59 GMT -5
I have same problem from what i tried tightening all body plastic panels and it did not go away, however i noticed something fun when removed the seat today one of the bolts of the engine cooling plastic cover was vibrating because i could not tight it up and entire plastic cover was vibrating pretty bad as well.
I had variator belt removed when trying, yeah i had variator on and belt removed so i assume my variator gears got sideways and out of balance as well.
Very similar but stronger noise i experienced when i had when my headlights loosen up and vibrating during ride. Another observation it kind of more i just start and gets better when scoot warms up. Another clue i noticed when removed my muffler there were few tiny metal pieces loose inside it could be them making noise. Its very tough to tell where it coming from it feels like from the front, but could be resonating trough the empty space inside plastic panels, perhaps if i connect phone in voice recorder mode in different parts of my scooter front, rear, center and try riding under same conditions then see where its loudest.
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Post by Sir Scoots-A-Lot on Jul 22, 2018 17:26:33 GMT -5
Thanks for the replies guys. It sounds like you had some real bad luck buying a new clutch Bill, but I'm glad you finally sorted it out. I will try testing my clutch on the stand soon. I know when I push my scoot with the engine off it makes a grinding noise sometimes but usually only when turning the steering so I thought it was just brakes hanging up... My clutch also feels like it has trouble grabbing the bell housing if I rev it too high off the line my acceleration will start really jerky most times then be fine after the first 5 or so mph.
Thanks again! -Presto
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Post by Sir Scoots-A-Lot on Jul 22, 2018 17:38:10 GMT -5
Kat and Pepi-- it would be helpful if you can maybe get video of the noise on the stand, maybe try to move the camera around and rev the engine up-- get someone to help you move around to shoot video/audio of every part of the bike and rev engine. Maybe take off your cvt cover and bendix starter gear so you can run the engine, rev it up and listen to the cvt side.
I initially had wheel bearings on my list of things that could cause the noise but if it happens on the stand it can't be wheel related.
I plan on taking off my exhaust this week to look for restrictions there and drill oullthe smaller diameter restrictor often located near where exhaust bolts to engine if present. Then i will inspect my muffler heat shield and anything else around exhaust to see if high engine rpm could be vibrating something...
I am starting to lean towards something valve, piston, con rod and or engine/transmission bearing related because it happens on the stand when not moving and only near top speed at high rpm. Maybe it is a speed restriction of some weird type? Because it only starts to happto to me at like 36-38 mph on basically flat ground and my scoot won't get any faster than 41.8mph gps so far even on downhills although maybe soon I will gps it on a steep 1/4 mile downhill to verify my apparent speed limitation.
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pepi
Scoot Junior
Posts: 8
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Post by pepi on Jul 22, 2018 19:55:41 GMT -5
Yes, I will get a video of the noise. I had too much going on today and now work is going to be really busy. But I will try to get it sooner than later. How can you take off the cvt cover and the bendix starter and still run the motor? No way of starting it. I did start it and run it for a second or two with the cover off, but I know that was dangerous because if the bendix starter dropped, Oh boy that would have been bad, . Karl
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Post by Sir Scoots-A-Lot on Jul 24, 2018 20:52:38 GMT -5
Your scoot does not have a kick starter Pepi? Most 49cc 149qmb do that I am aware of. Kick starting can be a pain-- I bought my scoot with a bad battery 1 month ago, didn't replace the battery for 2 weeks and felt like I broke or sprained part of my foot...
I noticed 49ccscoot.com member Bill who goes by the handle Piratelabs (and he posted on this thread) he posted a thread entitled Cyclic Vibration in General Scoot Chat. I am wondering if his sound is the same as ours? Sounds similar by description. The last post in that thread was someone saying something interesting that basically the variator and cvt may be out of balance. And Brent ( handle 90GTVERT & wise administrator of this site) posted on that thread it could be a bent primary drive shaft like on his Tao Tao but I never heard any follow up on that possibility. Although Pepi your noise was present with no drive belt on correct? So that would I guess eliminate the out of balance cvt theory and bent primary drive theory ( i think primary drive shaft is the by the clutch? Or os tge) if it happens with your drive belt off....leaving me guessing the problem could be the variator shaft/ bearings, another engine bearing or possibly a valve piston conrod crank or the exhaust...or anything else... A little frustrating. ...but oh well
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Post by GrumpyUnk on Jul 26, 2018 8:38:20 GMT -5
Anecdotally, had a bad cllutch that had broken ears where the pins attach the shoes to the pivot pin.
That thing would shake terribly if run up while on the stand. I found pieces of the clutch shoe metal in the CVT cover and wondered what they could be. New complete clutch and all is well. tom
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pepi
Scoot Junior
Posts: 8
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Post by pepi on Jul 27, 2018 20:21:31 GMT -5
Your scoot does not have a kick starter Pepi? Most 49cc 149qmb do that I am aware of. Kick starting can be a pain-- I bought my scoot with a bad battery 1 month ago, didn't replace the battery for 2 weeks and felt like I broke or sprained part of my foot... I noticed 49ccscoot.com member Bill who goes by the handle Piratelabs (and he posted on this thread) he posted a thread entitled Cyclic Vibration in General Scoot Chat. I am wondering if his sound is the same as ours? Sounds similar by description. The last post in that thread was someone saying something interesting that basically the variator and cvt may be out of balance. And Brent ( handle 90GTVERT & wise administrator of this site) posted on that thread it could be a bent primary drive shaft like on his Tao Tao but I never heard any follow up on that possibility. Although Pepi your noise was present with no drive belt on correct? So that would I guess eliminate the out of balance cvt theory and bent primary drive theory ( i think primary drive shaft is the by the clutch? Or os tge) if it happens with your drive belt off....leaving me guessing the problem could be the variator shaft/ bearings, another engine bearing or possibly a valve piston conrod crank or the exhaust...or anything else... A little frustrating. ...but oh well Yes, it has a kick start, but that is attached to the cover. I took a video of it today and am going to try and post it, along with pictures of the clutch. I took the cvt off to put the new belt on because I couldn't get it over the flywheel. I did notice one of the cvt rollers has a nick in it, but wouldn't think that would cause this, but I don;t know for sure. I also took the clutch apart and looked at that and thought it didn't look too bad. It does look like it got hot at one point because it is a little blueish in color. With the new belt It didn't seem as if it made the noise while drive at full throttle right away, but going up a hill I was luck to get 15 MPH, and then on flat surface, I could hear the noise again. Let's see if I can post everything now....
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pepi
Scoot Junior
Posts: 8
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Post by pepi on Jul 27, 2018 20:31:05 GMT -5
Here is the video, hopefully it works. You can hear me rev it a couple of times and you will hear the vibration and notice the bike wants to move.
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Post by Sir Scoots-A-Lot on Jul 30, 2018 18:11:21 GMT -5
Here is the video, hopefully it works. You can hear me rev it a couple of times and you will hear the vibration and notice the bike wants to move. Pepi what brand scooter do you have? Are you the first owner? Is it long case with 10 bolts on the cvt cover or short case with 8 bolts? Were you able to see the numbers on the old belt and get the same exact size? That sounds like the same noise I have. Im guessing just by the noise you have a long case and a 729 17.7 30 belt...?
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Post by Sir Scoots-A-Lot on Jul 30, 2018 18:27:20 GMT -5
I ask all this Pepi because I have a long case with that size belt 729 17.7 30....and one of my new theories is the noise is the long belt slapping the case! My belt is so long that when I take off the cvt cover (with scooter off of course!) I can squeeze the middle top and bottom of the belt in the middle of cvt between variator and clutch together fairly easily especially if I first pull the clutch together in back.
Maybe the noise would go away if we either got shorter belts and or checked to make sure our variators and clutche are able to open and close all the way. If you look at the variator and clutch plate faces where the belt rides on it you will notice the belt wears on the metal there and that will tell you how high and low the belt rides. You can also mark these faces with marker and then run the engine then open it up to look at the marker marks again to give you a more exact answer on belt travel. Mine look like the belt almost travels all the way to the outside of the variator but looks like maybe there is a little more room to go. Maybe i could get it to travel all the way with a different drive boss on the variator or by checking if I have a slightly restricrive washer although my washer must not be too bad because my scoot goes about 40 flat ground and I think its stock other than air filter although im not the 1st owner so not sure.
Sorry post is sooo long but my theory is it's belt slap due to a belt maybe slightly too long as I have noticed many many many size variations on 139qmb belts even though there are only 3 stock case sizes im aware of short lon and x-long. The belt length plus maybe a variator/clutch that aren't fully stretching the belt could cause xtra slack and at highest speed belt slap! What do you think Pepi? Thats why I wanted you to run witb no cover but looking at your starter I guess I will have to put shims under my short center stand to get my back wheel off the ground and try to get video evidence tomorrow evening or whenever
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pepi
Scoot Junior
Posts: 8
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Post by pepi on Jul 30, 2018 20:56:08 GMT -5
It is a Kaitong MD50QT-9. My daughter just bought it used, I forget how many miles on it. It is a long case and the belt is a 729-17.7-30, and I just bought a new Kevlar belt. I don't think belt slap because it does it without the belt on. I remove the belt and put the cover back on so I can start it and run it. I am thinking about getting a tachometer and see what RPM's it is doing it at.
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Post by Sir Scoots-A-Lot on Jul 31, 2018 16:53:56 GMT -5
Darn! My theory was foiled again because I forgot you already ran it with the belt off...and you tested it standing still which eliminates wheel noises or plastics making sounds in the wind Brings me back to piston/wrist pin, valves, an engine bearing, part of the variator or possibly exhaust although I feel like exhaust is unlikely because if i get off the accelerator down a steep hill when it makes the noise and then barely touch the throttle again it instantly makes the noise..so your tachometer idea sounds excellent and I heard they are sold fairly cheap. Two reasons I am sooo fixed on solving this mystery is 1) is my scoot going to break if I keep pushing ot to this speed? 2) Is this noise an indication of some speed limiting factor in either the design of the scooter so it can't practically go faster or a speed restriction purposefully placed? I wonder these because I want to put a big bore kit on but of my scoot isn't liking going any faster at all then it defeats half the purpose of upgrading
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Post by GrumpyUnk on Aug 1, 2018 12:10:31 GMT -5
Given the parts that are possibilities, I'd substitute another variator as it is the easiest part to change. If that doesn't reduce/eliminate the vibration, it must be crankshaft/rod/piston.
You could remove the movable parts of the variator, leaving only the shell with the ramps, and see if the rollers or inner plate are the cause. tom
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