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Recently replaced my rattley clutch and noticed that the drive belt makes a slapping noise at idle.
Is this normal and what causes this. It is a new malossi belt. I sanded the drive faces with 80grit.
I have a video but can't seem to get it uploaded.
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they generally don't slap much or often at idle. I'd pull everything apart and double check the part number on the belt and make sure that everything in assembled correctly.

have you run it at all, or just idling on the center stand and not much else?
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Probably put 20 miles on it . Used the Malossi belt kit that came with rollers and the yellow spring seat. Also used the malossi white contra spring. I sanded the drive faces, maybe more than breaking the glaze. Belt is not sitting on the spacer in the front.
1 thing tho, I did not pay attention to the belt direction when installing it new. Not sure if that matters. It did smell a little like burning rubber the for a little bit of running on the stand.
Is there a certain way to line up the front variator and starter gear? I see an arrow on the starter gear but couldn't find anything about it in the manual.


What is the best way to post a video here?
⚠️ Last edited by smoker on UTC; edited 1 time
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smoker wrote:
Probably put 20 miles on it . Used the Malossi belt kit that came with rollers and the yellow spring seat. Also used the malossi white contra spring. I sanded the drive faces, maybe more than breaking the glaze. Belt is not sitting on the spacer in the front.
1 thing tho, I did not pay attention to the belt direction when installing it new. Not sure if that matters. It did smell a little like burning rubber the for a little bit of running on the stand.
Is there a certain way to line up the front variator and starter gear? I see an arrow on the starter gear but couldn't find anything about it in the manual.


What is the best way to post a video here?
the belt goes on so that you can read the letters/numbers left to right or the arrows point to the left.

the front 1/2 pulley has a "tick mark" off one of the fins that lines up with the
ring gear. make sure that the rubber dampening ring is in good condition along with the ring gear.

be sure that the belt is not pinched between the vario and 1/2 pulley once torqued up-- just because it's not on the pin doesn't mean that it's not pinched. you should be able to rotate the clutch and the belt should slip across the pulleys.

check the condition of the idler pulley. if the bearing is bad or the pulley itself is somehow damaged the belt won't glide across it and winds up making a bunch of racket.

the burning rubber smell is no bueno. not the end of the world, but something might be wrong and that's worth investigating.
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What is the significance of the belt direction? On automotive belts you want to keep it going in the same direction as it was installed when it was new. It doesn't matter which way they go on when they are new. Kinda like tires. Is this the same with drive belts? Or are they manufactured to only work in one direction.
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Here is a video of it on youtube
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Seems like the belt noise is coming from the roller. It spins freely but dry ish. Popped the seal off and greased it. It is quieter now . When on a 20-30 ride with a passenger and seems fine. A little tick now and then at idle. Gonna roll with it an see.
Thanks for the advise.
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smoker wrote:
Here is a video of it on youtube
interesting that in another recent thread we were talking about the danger of running the engine with the cover off the transmission
⚠️ Last edited by SteelBytes on UTC; edited 1 time
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First of all, there is no danger in running it with the cover off, IF you keep your hands out of it. I've done it many times. Way back in 2012 I bought a Yamaha Zuma 125. I joined a Zuma forum. Several members there were running their scooters without the CVT covers. Some aftermarket place sold a guard called an "anklebiter" that would prevent you from getting your foot into the CVT but still leave it basically open. I personally believe the CVT needs to be protected from dirt. Here's one on a Zuma 125

Yes, they actually rode them that way.

As far as the issue with your GT200, mine is very quiet at idle. The rear wheel does turn slowly on the centerstand. It will also make rattling noises when you rev it up on the centerstand, then release the throttle. That is normal. When you rev it up and the clutch engages, the belt is under tension. When you release the throttle, it releases the tension on the belt, and it will flap around for a few seconds until the pulleys slow down to idle speed. I really don't know what is going on with yours, I've never seen that before. I have only used Vespa belts on mine. That plastic pulley in the middle is loose, most CVT scooters don't even have it. It's basically intended as a damper, something for the belt to hit when it does flap around a little. It could be the wrong belt, or the idle could be set too high. I understand how a CVT works, but I have never messed with them or modified them, just replaced belts and rollers, so I am not familiar with some of their intricacies.
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SteelBytes wrote:
interesting that in another recent thread we were talking about the danger of running the engine with the cover off the transmission
yet people do it all the time. what's to stop the clutch bell from slipping off? or the bendix from falling into the ring gear?

nothing, that's what.
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VintageScooterDude wrote:
First of all, there is no danger in running it with the cover off, IF you keep your hands out of it. I've done it many times. Way back in 2012 I bought a Yamaha Zuma 125. I joined a Zuma forum. Several members there were running their scooters without the CVT covers. Some aftermarket place sold a guard called an "anklebiter" that would prevent you from getting your foot into the CVT but still leave it basically open. I personally believe the CVT needs to be protected from dirt. Here's one on a Zuma 125

Yes, they actually rode them that way.

As far as the issue with your GT200, mine is very quiet at idle. The rear wheel does turn slowly on the centerstand. It will also make rattling noises when you rev it up on the centerstand, then release the throttle. That is normal. When you rev it up and the clutch engages, the belt is under tension. When you release the throttle, it releases the tension on the belt, and it will flap around for a few seconds until the pulleys slow down to idle speed. I really don't know what is going on with yours, I've never seen that before. I have only used Vespa belts on mine. That plastic pulley in the middle is loose, most CVT scooters don't even have it. It's basically intended as a damper, something for the belt to hit when it does flap around a little. It could be the wrong belt, or the idle could be set too high. I understand how a CVT works, but I have never messed with them or modified them, just replaced belts and rollers, so I am not familiar with some of their intricacies.
surprising that as a mechanic of a million years that you fail to see how the clutch is secured on a vespa v. zuma and exactly why that is a bad idea and inherently dangerous.
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I totally agree that it is a bad idea to RIDE any scooter with the CVT cover off. But running it that way while working on it should not be a problem. And yes, there is a difference between the way the clutch bell is held on on a Vespa GT200 and early GTS250s and GTS300s compared to most Asian scooters. And yes, I just now realized that. The Vespa has a bearing in the CVT cover which presses against the clutch bell and keeps it in place. Without the CVT cover, simply installing the nut on the rear shaft will not hold the clutch bell in place. The GT200 is my first Vespa. All my other scooters, except the Genuine Stella, were Asian. I do not claim to be a scooter expert. But in looking at the Vespa design, all you would have to do is put a spacer on the shaft between the clutch bell and the nut to hold the clutch bell in place without the cover. Which just made me realize that could be part of the problem in the video. I can't tell if the clutch bell is being held securely in place while the engine is running or not. If it isn't, that could be the problem, or part of the problem, if the clutch bell is loose on the shaft.
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My clutch bell needs a gear puller to get off. I am assuming the it is because of it previously being over tightened ( if it is supposed to slip off easily) . This one however does not. I did not ride the scooter with the cover off. The vespa uses a support bearing for the clutch drive spindle and starter.
Definitely DO NOT DRIVE THE SCOOTER WITHOUT THE VARIATOR COVER ON. BAD THINGS WILL HAPPEN. AND WILL EAT FINGERS. BAD BAD BAD.
I was merely investigating the noise under a controlled environment.
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Also crankshaft endplay on this bike seems excessive. The crank may be walking and the belt is bouncing off each side of the drive faces causing the belt bounce. If this was an Audi or Volkswagen engine (it's what I do professionally for 20 years) the thrust bearings would be wasted and would warrant a new crank and bearings.
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running it without the shaft supported also puts strain on the bearings and seals of both the pulley and shaft. these are now seeing directional forces they were not intended to. think about the weight of those components and how much leverage is being exerted there.

so, if you have noisy bearings or leaky seals in that area down the line you'll know why.
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Once you have the CVT cover off, the clutch bell should just pull off. Mine did. The bearing in the CVT cover and the nut hold it on, once those are removed, there shouldn't be anything else holding it on. Only thing I can think of is the clutch shoes are pressing against it or the splines might be damaged. If you can hold the clutch bell with your hand with the engine off, and turn the rear wheel, then the clutch shoes are not holding it.

"I was merely investigating the noise under a controlled environment" That is what I have been trying to say. Don't ride the scooter with it off. But it is ok to run the engine with the cover off, as long as the proper precautions have been taken. On a Vespa, you do need to install a spacer (maybe a stack of washers or a nut of the proper size) between the clutch bell and the nut to take the place of the bearing in the CVT cover so the clutch bell is held on properly. This is ONLY for test purposes, so you can observe what is going on under the cover. That bearing in the CVT cover is there to hold the left end of the rear shaft in place.

As for crankshaft end play, I wouldn't think there should be enough to notice, but that could be wrong. I have the GT200 service manual, I can check to see what the crankshaft end play should be, IF it is listed. Is there any radial (side to side) play in the crankshaft? I have never had a Vespa engine apart. But all crankshafts have either a radial thrust bearing, or in the case of most car engines, several radial bearings and one thrust bearing, to control both end play and radial play.

EDIT: Crankshaft end play is listed in the manual as 0.005-0.015 in. Not very much at all. If there is obvious endplay, there is likely a problem.
⚠️ Last edited by VintageScooterDude on UTC; edited 1 time
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VintageScooterDude wrote:
Once you have the CVT cover off, the clutch bell should just pull off. Mine did. The bearing in the CVT cover and the nut hold it on, once those are removed, there shouldn't be anything else holding it on. Only thing I can think of is the clutch shoes are pressing against it or the splines might be damaged. If you can hold the clutch bell with your hand with the engine off, and turn the rear wheel, then the clutch shoes are not holding it.
stuck clutch bells are fairly common. debris or rust on the splines can lock them on. overheating the clutch bell can also warp it and cause difficulty in removal. over torquing the clutch nut only strains the shaft and damages the bearings which is not good, but won't lock the bell to shaft.

if you're holding the bell and rotate the wheel, it is a direct connection and it will turn. the clutch shoes will only engage the bell at RPM due to centrifugal force unless something is broken in the clutch pack.
Quote:
As for crankshaft end play, I wouldn't think there should be any, but that could be wrong. I have the GT200 service manual, I can check to see what the crankshaft end play should be, IF it is listed. Is there any radial (side to side) play in the crankshaft? I have never had a Vespa engine apart. But all crankshafts have either a radial thrust bearing, or in the case of car engines, several radial bearings and one thrust bearing, to control both end play and radial play.
there's no bearings, only thrust washers. the only bearing on a vespa bottom end is the rod bearing. a bit of end play is fairly typical on these.
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And for the record, I can fix anything....Eventually.
Depending on your definition of fix.
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