Modern Vespa

Hello everyone I am new to the world of piaggio MP3, my first ever Italian scooter/ trike , What can I say it's an absolute blast to ride, and I was surprised how much like a 2 wheeler it feels to ride .
I would just like to ask some advice please if a may?
I bought it brand new in July this year from a local dealer , it has covered 850 miles now and went in for its 600mi interim service , not long after that I started to notice a little squeak when I pulled away , not every time but I got progressively worse as time went on , so naturally I returned it to the dealer who had it for a couple of days and informed me that there was dirt ingress in the drive belt pulley and they cleaned it out and the squeak has stopped after an extensive test ride.
So I picked it up and went for a ride the next day , all felt fine , but low and behold 30 miles later the drive belt squeak is back...( like before only on acceleration)
I'm I bit miffed really, is the dealer spinning me a yarn , surely you can ride these all year round and not have to worry about getting dirt ingress on the drive belt through the case breathers.
Has anyone else had this problem?
Any advice would be greatly appreciated.

From what I've read this noise could came from the clutch bell which some times get dirty from ferodo deposits and you can hear this squeaky noise.
At traffic lights try to start fast and see if it happens again...

That is exactly when it happens on acceleration from a stand still , once you are up and running it is fine , thanks for the advice Ontheroad 65

Is it something to be concerned with, should a brand new bike be making noises like this, or should I be poking back into the dealers again to sort out!!!

It's a glazed clutch drum and pads. Often times the glazed clutch drum is caused by being too cautious on take-off. It's not that bad in and of itself, but it's indicative of something slightly wrong and should be treated. If it bothers you, you can do two things:

1) Deglaze the clutch yourself. Sometimes it works to rev the engine with the brake on and make the clutch smoke a bit (30 seconds only). But the best way is to remove it and hit the pads and the drum surfaces with 600-grit sandpaper, leaving a light cross-hatch. This will allow the surfaces to slide by each other without rapidly "grabbing" and releasing, which is the sound you hear.
2) Then prevent it occurring again by making it a point to accelerate more rapidly, then back off when you're up to speed. This is the best way to help the clutch from wearing out as fast, too. Slow acceleration puts a lot of stress on the clutch since it remains partially engaged for long periods, leading to glazing (which is essentially polishing itself) and increased wear. You want to avoid making the clutch polish itself- think of polishing your silverware- you want to avoid long periods of light pressure. Short periods of heavy pressure is better.

I doubt the dealer did more than just hit the variator with a shot of air. Which, rather than removing the offending dust from the clutch, actually blew a little dust between the clutch pads and the surface. That dust kept the clutch from grabbing for a few miles until it wore away and the polished surfaces could fully contact each other, but it didn't do anything about the glaze. He really needed to deglaze the clutch, which requires its removal to do correctly.

Thanks for the advice Squeazel, I reckon it is exactly that, and you are correct the dealer had it back for a week , took it on two test rides and come to the conclusion there is nothing wrong , no squeaks on acceleration: but guess what I picked it up today , within 100 yards a squeak on acceleration, it's a bit intermittent at the moment so I will wait for it to get worse then see if they will do anything about it. But I looks like I'm better off doing myself but I'm holding off doing anything as I don't want to void the warranty.......watch this space!

Well, you can try the burnout trick if it's annoying you- 20-30 seconds of trying to accelerate while holding the rear brake. Then ride as normal for a little while to let the clutch cool down gently so it doesn't warp. On my Burgman 400, they called it the "strangled seal" noise, and it was pretty common. It's not dangerous and doesn't affect longevity much, other than being an indicator of a rider that's being maybe a little too gentle in their acceleration. But sometimes it goes away as the clutch wears, too.