Modern Vespa

just stripped my gts 125 down for the fifth time now and still no joy. it was only a roller and belt change! now for some reason every time i put it back together that noise is still there like a knocking but only on tickover a few revs and it goes any ideas please......dean..... p.s. i made sure the belt was right to the bottom of the pullies...

Does the scoot run okay?
My GT200 always has a 'snapping' kind of sound on idle running that
it didn't have when the scoot was brand new.
But at alsmost 3K miles the scoot still runs beautifully,
so I've decided not to overly worry about the sound.
It's prolly natural, I'm thinking now.

When you changed the belt and rollers, did you use new stockers?
Because IMO sometimes aftermarket "improvement" accessories turn out to be anything but..!

the only noise before i started was a slight rattle from the rollers thats why i changed them and the scooter was running great till i messed. i only ever used genuine vespa parts from my local dealer! so what have i done wrong???????.........

Hmm... maybe that's the problem... you said "pullies" (plural).

The belt should indeed be at the bottom of the clutch (driven) pulley when reassembling, but it should be at the TOP of the variator (driving) pulley and not holding the pulley halves apart when the nut is re-tightened. If you tighten the nut down so that the belt is squeezed between the pulley halves, the whole assembly will loosen up as soon as the engine is started.

but if the the belt is at the bottom of the clutch pully then i have no say where the belt is on the drive pully or do i???

Forcing the belt into the bottom of the clutch pulley gives you the slack to allow the belt to rise to the top rim of the variator pulley. But you still need to ensure that the belt is not being pinched between the variator pulley halves when you tighten the nut. If you deliberately positioned the belt in the bottoms of BOTH pulleys, then the belt would have been very slack in between the pulleys, and you would have indeed tightened the nut against the belt instead of the hard stop... a definite no-no.

When the variator nut is tightened, the two halves of the variator pulley should be pulled together against the hard stop (not the belt), and the belt should just be lying slackly near the top rim of the variator pulley, not being pinched.

ok i'll try it now thanks for your help fingers crossed.......

my god this is doin' my head in now! just put everything back together again making sure the belt was at the bottom of the clutch pully giving me enough slack for the drive pully. i then tightened every down on the drive pully then checked and the belt was free and not trapped. great, keeping my fingers crossed i finished putting everything else back together. i started the engine and its still the same..... i pulled it apart again and the belt was at the top of the clutch pully and at the bottom of the drive pully is this right????i just can't understand whats happening please help!!!

That is what it is supposed to do. Once the engine has been turned over and the belt settles in, the big contra (or torque driver) spring in the clutch assembly forces the two halves of the clutch pulley together at idle (causing the belt to rise to the top of that pulley) and pulling the variator pulley halves apart (allowing the belt to drop to the bottom). That is the lowest gear ratio, and the way things are supposed to be at idle, and that is how it will remain when the scoot is turned off.

As you rev the engine, the roller weights in the variator are flung outward by centrifugal force against the ramps in the movable half of the variator pulley, forcing the pulley halves together and causing the the belt to climb toward the rim of the variator pulley. Because the belt is a fixed length, this causes the belt to force the clutch pulley halves apart against the force of the contra spring. At this point, the transmission has fully shifted into high gear and will remain there until the engine speed decreases. When you let off the gas, the contra spring is stronger than the centrifugal force, so the clutch pulley closes, the weights drop back to the center of the variator, and the transmission returns to the low gear configuration.

Here is a video of a CVT transmission in operation with the transmission cover off (don't try this on a Vespa!):
http://www.youtube.com/watch?v=pjmv-dX2PWs&feature=related

What exactly is the problem you are observing? Your description sounds like normal operation at this point. Is it excessively noisy?

yes it is really noisey as if something is loose it is quite worrying!

???????

Am I not allowed to sleep? I'm trying to help you out, but you are doling out information in little dribs and drabs, making it difficult to do so.

If the variator nut was tightened without pinching the belt, then the noise is likely the result of one of two things:

1. you reassembled the parts in the wrong order (got a spacer out of place or something) causing belt misalignment, or
2. you either got the rollers in the variator backwards or you allowed at least one of them to slip out of place as you put the variator back on the shaft (possibly got turned sideways). It's also possible one or more of the little V-shaped plastic slide bushings fell off as you were reassembling it.

You might try being a little more patient and considerate with someone who is trying to help you out without the benefit of much in the way of useful descriptions or pictures.

sorry if i am keeping you awake thats honestly what i did not mean to do, its that you are the only person that has helped me out, all my m8s are into all the old stuff (two strokes) they haven't got a clue!! all my local scooter shops will not help either they just want my hard earned and will not give me any info'. i have just started from the top again and reassembled everything from the start being extra carfull double checking every last thing, and still its the same....so it looks like a trip to the scooter shop....dean

Its a motorised vehicle. It is bound to make a bit of noise. Are you sure your not worrying over nothing?

If it worries you that much then take it to a garage and get them to look at it.

its booked in monday morning thanks for all your help cheers dean....