Modern Vespa

Hi guys, every so often when I hit the throttle, I get the most grotesque noise like gears really grinding. I am not really even going that fast. Then I let up on the throttle and then hit the throttle again and the sound goes away.
It does not happen 100 per cent of the time. What should I do?
Has this happened to anyone else?

All the time and for nearly everybody. Check the rest of the web site about seals, (marine Mammals) grinding, graunching and other extraneous noises.

somebody wiser than I will tell you what it is caused by.

I don't imagine that the "strangled sealion" clutch sound has a metallic component, which I associate with grinding gears. Scootercrazy, can you describe the sound more precisely?

With no miles listed, I would suspect the idle belt pulley bearings first.

Happens quite often, especially if forced to move slowly through a traffic jam or uphill: https://modernvespa.com/forum/topic47765

I'm planning to install J-Costa variator to get rid of the sound, as the sound apparently caused by the very same detail J-Costa replaces...

It is a loud, grinding sound--ungodly, really--but I read the comments below and also followed a link someone provided and it really sounds like that glazing issue. So, full throttle we go. I will see whether that works. And then the J Costa Variator.....
I have only about 3000 kms on my bike.
And have to take it in for servicing in the next month.
Many thanks for all your help.

Thanks for the link. I think this is exactly what is happening. Going to try what is recommended. Fulll throttle take offs etc.
Many thanks.